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data-target="#ref48251"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/The-discovery-of-isotopes#ref48251">Radioactive isotopes</a></li><li data-target="#ref48252"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Elemental-and-isotopic-abundances">Elemental and isotopic abundances</a></li><li data-target="#ref48253"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances">Variations in isotopic abundances</a><ul data-level="h2"><li data-target="#ref48254"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances#ref48254">Radioactive decay</a></li></ul><ul data-level="h2"><li data-target="#ref48255"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances#ref48255">Mass fractionation</a></li></ul><ul data-level="h2"><li data-target="#ref48256"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances#ref48256">Other causes of isotopic abundance variations</a></li></ul></li><li data-target="#ref48257"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances#ref48257">Physical properties associated with isotopes</a></li><li data-target="#ref48258"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Variations-in-isotopic-abundances#ref48258">Effect of isotopes on atomic and molecular spectra</a><ul data-level="h2"><li data-target="#ref48259"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Molecular-vibrations">Molecular vibrations</a></li></ul><ul data-level="h2"><li data-target="#ref48260"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Molecular-vibrations#ref48260">Importance in the study of polyatomic molecules</a></li></ul></li><li data-target="#ref48261"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Molecular-vibrations#ref48261">Chemical effects of isotopic substitution</a></li><li data-target="#ref48262"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Molecular-vibrations#ref48262">Effect of isotopic substitution on reaction rates</a></li><li data-target="#ref48263"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment">Isotope separation and enrichment</a><ul data-level="h2"><li data-target="#ref48264"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48264">Mass spectrometry</a></li></ul><ul data-level="h2"><li data-target="#ref48265"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48265">Distillation</a></li></ul><ul data-level="h2"><li data-target="#ref48266"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48266">Chemical exchange reactions</a></li></ul><ul data-level="h2"><li data-target="#ref48267"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48267">Gaseous diffusion</a></li></ul><ul data-level="h2"><li data-target="#ref48268"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48268">Gas centrifugation</a></li></ul><ul data-level="h2"><li data-target="#ref48269"><a href="/web/20200509141434/https://www.britannica.com/science/isotope/Isotope-separation-and-enrichment#ref48269">Photochemical enrichment methods</a></li></ul></li></ul></div> </div> <div class="grid-xs"> <div class="infinite-pagination-container container"> <h1>Isotope</h1> <div class="topic-identifier">chemistry</div> <div class="md-byline"> <div class="written-by"> <span>Written By: </span> <ul> <li><a href="/web/20200509141434/https://www.britannica.com/contributor/Gregory-F-Herzog/3392">Gregory F. Herzog</a></li> </ul> </div> <div class="last-updated"> <span>Last Updated: </span> <time datetime="2020-04-09"> Apr 9, 2020</time> <a data-type="accordion-link" href="#accordion-article-history" rel="nofollow">See Article History</a> </div></div> <div class="grid gutter-right"> <div class="grid-sm pr-lg-60"> <span class="marker before-article"></span><section id="ref1" data-level="1"><p><strong><span id="ref496298"></span>Isotope</strong>, one of two or more species of <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atom" class="md-crosslink">atoms</a> of a <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/chemical-element" class="md-crosslink autoxref">chemical element</a> with the same <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atomic-number" class="md-crosslink">atomic number</a> and position in the <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/periodic-table" class="md-crosslink">periodic table</a> and nearly identical chemical behaviour but with different <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atomic-mass" class="md-crosslink">atomic masses</a> and physical properties. Every chemical element has one or more isotopes.</p><span class="marker p1"></span><span class="marker AM1 am-inline"></span><span class="marker MOD1 mod-inline"></span><p>An <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atom" class="md-crosslink autoxref">atom</a> is first identified and labeled according to the number of <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/proton-subatomic-particle" class="md-crosslink">protons</a> in its nucleus. This <span id="ref496299"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atomic-number" class="md-crosslink">atomic number</a> is ordinarily given the symbol <em>Z</em>. The great importance of the atomic number derives from the observation that all atoms with the same atomic number have nearly, if not precisely, identical chemical properties. A large collection of atoms with the same atomic number <a href="https://web.archive.org/web/20200509141434/https://www.merriam-webster.com/dictionary/constitutes" class="md-dictionary-link md-dictionary-tt-off" data-term="constitutes">constitutes</a> a sample of an element. A bar of pure <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/uranium" class="md-crosslink">uranium</a>, for instance, would consist entirely of atoms with atomic number 92. The periodic table of the elements assigns one place to every atomic number, and each of these places is labeled with the common name of the element, as, for example, <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/calcium" class="md-crosslink">calcium</a>, <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/radon" class="md-crosslink">radon</a>, or uranium.<span class="inline-youtube-video d-print-none"><iframe class="" width="560" height="315" allow="autoplay; encrypted-media" frameborder="0" allowfullscreen="allowfullscreen" src="https://web.archive.org/web/20200509141434if_/https://www.youtube-nocookie.com/embed/8_C5Au1pr6w?rel=0"></iframe></span></p><span class="marker p2"></span><span class="marker AM2 am-inline"></span><span class="marker MOD2 mod-inline"></span><p>Not all the atoms of an element need have the same number of <span id="ref496300"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/neutron" class="md-crosslink">neutrons</a> in their nuclei. In fact, it is precisely the variation in the number of neutrons in the nuclei of atoms that gives rise to isotopes. <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/hydrogen" class="md-crosslink">Hydrogen</a> is a case in point. It has the atomic number 1. Three nuclei with one proton are known that contain 0, 1, and 2 neutrons, respectively. The three share the place in the periodic table assigned to atomic number 1 and hence are called isotopes (from the Greek <em>isos</em>, meaning “same,” and <em>topos</em>, signifying “place”) of hydrogen.</p><span class="marker p3"></span><span class="marker AM3 am-inline"></span><span class="marker MOD3 mod-inline"></span><p>Many important properties of an isotope depend on its mass. The total number of neutrons and protons (symbol <em>A</em>), or <span id="ref496301"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/mass-number" class="md-crosslink">mass number</a>, of the nucleus gives approximately the mass measured on the so-called atomic-mass-unit (amu) scale. The numerical difference between the actual measured mass of an isotope and <em>A</em> is called either the mass excess or the <span id="ref496302"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/mass-defect" class="md-crosslink">mass defect</a> (symbol Δ; <em>see</em> <span id="ref1243"></span>table).</p><span class="marker p4"></span><span class="marker AM4 am-inline"></span><div class="marketing-INLINE_SUBSCRIPTION marketing-content" data-marketing-id="INLINE_SUBSCRIPTION"><div class="inline-subscription mb-30 mx-sm-20 font-16 text-center"> Get exclusive access to content from our 1768 First Edition with your subscription. <a href="https://web.archive.org/web/20200509141434/https://subscription.britannica.com/subscribe?partnerCode=BP_House_USD_A" class="cta">Subscribe today</a> </div></div><span class="marker MOD4 mod-inline"></span><span class="md-raw-html"><div class="md-drag md-table-wrapper"><table class=""> <caption class="">Abundances of the isotopes</caption> <thead class=""> <tr> <th scope="col">element</th> <th scope="col">Z</th> <th scope="col">symbol</th> <th scope="col">A</th> <th scope="col">abundance</th> <th scope="col">mass excess</th> </tr> </thead> <tfoot class=""> <tr> <td colspan="6">Sources: G. Audi and A.H. Wapstra, "The 1995 Update to Atomic Mass Evaluation," Nuclear Physics, A595:409–480 (1995); K.J.R. Rosman and P.D.P. Taylor, "Isotopic Compositions of the Elements 1997," J. Phys. Chem. Ref. Data, 27:1275–85 (1995).</td> </tr> </tfoot> <tbody class=""> <tr class="has-rs"> <td rowspan="" scope="row">hydrogen</td> <td>1</td> <td>H</td> <td>1</td> <td>99.9885</td> <td>7.289</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>2</td> <td>0.0151</td> <td>13.136</td> </tr> <tr> <td scope="row">helium</td> <td>2</td> <td>He</td> <td>3</td> <td>0.000138</td> <td>14.931</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>4</td> <td>99.999863</td> <td>2.425</td> </tr> <tr> <td scope="row">lithium</td> <td>3</td> <td>Li</td> <td>6</td> <td>7.59</td> <td>14.086</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>7</td> <td>92.41</td> <td>14.908</td> </tr> <tr> <td scope="row">beryllium</td> <td>4</td> <td>Be</td> <td>9</td> <td>100</td> <td>11.348</td> </tr> <tr> <td scope="row">boron</td> <td>5</td> <td>B</td> <td>10</td> <td>19.9</td> <td>12.051</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>11</td> <td>80.1</td> <td>8.668</td> </tr> <tr> <td scope="row">carbon</td> <td>6</td> <td>C</td> <td>12</td> <td>98.93</td> <td>0</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>13</td> <td>1.07</td> <td>3.125</td> </tr> <tr> <td scope="row">nitrogen</td> <td>7</td> <td>N</td> <td>14</td> <td>99.632</td> <td>2.863</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>15</td> <td>0.368</td> <td>0.101</td> </tr> <tr> <td scope="row">oxygen</td> <td>8</td> <td>O</td> <td>16</td> <td>99.757</td> <td>−4.737</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>17</td> <td>0.038</td> <td>−0.809</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>18</td> <td>0.205</td> <td>−0.782</td> </tr> <tr> <td scope="row">fluorine</td> <td>9</td> <td>F</td> <td>19</td> <td>100</td> <td>−1.487</td> </tr> <tr> <td scope="row">neon</td> <td>10</td> <td>Ne</td> <td>20</td> <td>90.48</td> <td>−7.042</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>21</td> <td>0.27</td> <td>−5.732</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>22</td> <td>9.25</td> <td>−8.024</td> </tr> <tr> <td scope="row">sodium</td> <td>11</td> <td>Na</td> <td>23</td> <td>100</td> <td>−9.529</td> </tr> <tr> <td scope="row">magnesium</td> <td>12</td> <td>Mg</td> <td>24</td> <td>78.99</td> <td>−13.933</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>25</td> <td>10.00</td> <td>−13.193</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>26</td> <td>11.01</td> <td>−16.214</td> </tr> <tr> <td scope="row">aluminum</td> <td>13</td> <td>Al</td> <td>27</td> <td>100</td> <td>−17.197</td> </tr> <tr> <td scope="row">silicon</td> <td>14</td> <td>Si</td> <td>28</td> <td>92.2297</td> <td>−21.493</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>29</td> <td>4.6832</td> <td>−21.895</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>30</td> <td>3.0872</td> <td>−24.433</td> </tr> <tr> <td scope="row">phosphorus</td> <td>15</td> <td>P</td> <td>31</td> <td>100</td> <td>−24.441</td> </tr> <tr> <td scope="row">sulfur</td> <td>16</td> <td>S</td> <td>32</td> <td>94.93</td> <td>−26.016</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>33</td> <td>0.76</td> <td>−26.586</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>34</td> <td>4.29</td> <td>−29.932</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>36</td> <td>0.02</td> <td>−30.664</td> </tr> <tr> <td scope="row">chlorine</td> <td>17</td> <td>Cl</td> <td>35</td> <td>75.78</td> <td>−29.014</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>37</td> <td>24.22</td> <td>−31.762</td> </tr> <tr> <td scope="row">argon</td> <td>18</td> <td>Ar</td> <td>36</td> <td>0.3365</td> <td>−30.230</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>38</td> <td>0.0632</td> <td>−34.715</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>40</td> <td>99.6003</td> <td>−35.040</td> </tr> <tr> <td scope="row">potassium</td> <td>19</td> <td>K</td> <td>39</td> <td>93.2581</td> <td>−33.807</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>40</td> <td>0.0117</td> <td>−33.535</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>41</td> <td>6.7302</td> <td>−35.559</td> </tr> <tr> <td scope="row">calcium</td> <td>20</td> <td>Ca</td> <td>40</td> <td>96.941</td> <td>−34.846</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>42</td> <td>0.647</td> <td>−38.547</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>43</td> <td>0.135</td> <td>−38.408</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>44</td> <td>2.086</td> <td>−41.469</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>46</td> <td>0.004</td> <td>−43.135</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>48</td> <td>0.187</td> <td>−44.215</td> </tr> <tr> <td scope="row">scandium</td> <td>21</td> <td>Sc</td> <td>45</td> <td>100</td> <td>−41.069</td> </tr> <tr> <td scope="row">titanium</td> <td>22</td> <td>Ti</td> <td>46</td> <td>8.25</td> <td>−44.125</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>47</td> <td>7.44</td> <td>−44.932</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>48</td> <td>73.72</td> <td>−48.487</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>49</td> <td>5.41</td> <td>−48.558</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>50</td> <td>5.18</td> <td>−51.426</td> </tr> <tr> <td scope="row">vanadium</td> <td>23</td> <td>V</td> <td>50</td> <td>0.250</td> <td>−49.218</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>51</td> <td>99.750</td> <td>−52.198</td> </tr> <tr> <td scope="row">chromium</td> <td>24</td> <td>Cr</td> <td>50</td> <td>4.345</td> <td>−50.254</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>52</td> <td>83.789</td> <td>−55.413</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>53</td> <td>9.501</td> <td>−55.281</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>54</td> <td>2.365</td> <td>−56.928</td> </tr> <tr> <td scope="row">manganese</td> <td>25</td> <td>Mn</td> <td>55</td> <td>100</td> <td>−57.706</td> </tr> <tr> <td scope="row">iron</td> <td>26</td> <td>Fe</td> <td>54</td> <td>5.845</td> <td>−56.248</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>56</td> <td>91.754</td> <td>−60.601</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>57</td> <td>2.119</td> <td>−60.176</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>58</td> <td>0.282</td> <td>−62.149</td> </tr> <tr> <td scope="row">cobalt</td> <td>27</td> <td>Co</td> <td>59</td> <td>100</td> <td>−62.224</td> </tr> <tr> <td scope="row">nickel</td> <td>28</td> <td>Ni</td> <td>58</td> <td>68.0769</td> <td>−60.223</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>60</td> <td>26.2231</td> <td>−64.468</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>61</td> <td>1.1399</td> <td>−64.217</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>62</td> <td>3.6345</td> <td>−66.743</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>64</td> <td>0.9256</td> <td>−67.096</td> </tr> <tr> <td scope="row">copper</td> <td>29</td> <td>Cu</td> <td>63</td> <td>69.17</td> <td>−65.576</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>65</td> <td>30.83</td> <td>−67.260</td> </tr> <tr> <td scope="row">zinc</td> <td>30</td> <td>Zn</td> <td>64</td> <td>48.63</td> <td>−66.000</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>66</td> <td>27.90</td> <td>−68.896</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>67</td> <td>4.10</td> <td>−67.877</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>68</td> <td>18.75</td> <td>−70.004</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>70</td> <td>0.62</td> <td>−69.559</td> </tr> <tr> <td scope="row">gallium</td> <td>31</td> <td>Ga</td> <td>69</td> <td>60.108</td> <td>−69.321</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>71</td> <td>39.892</td> <td>−70.137</td> </tr> <tr> <td scope="row">germanium</td> <td>32</td> <td>Ge</td> <td>70</td> <td>20.84</td> <td>−70.560</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>72</td> <td>27.54</td> <td>−72.586</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>73</td> <td>7.73</td> <td>−71.299</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>74</td> <td>36.28</td> <td>−73.422</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>76</td> <td>7.61</td> <td>−73.213</td> </tr> <tr> <td scope="row">arsenic</td> <td>33</td> <td>As</td> <td>75</td> <td>100</td> <td>−73.032</td> </tr> <tr> <td scope="row">selenium</td> <td>34</td> <td>Se</td> <td>74</td> <td>0.89</td> <td>−72.213</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>76</td> <td>9.37</td> <td>−75.252</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>77</td> <td>7.63</td> <td>−74.599</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>78</td> <td>23.77</td> <td>−77.026</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>80</td> <td>49.61</td> <td>−77.759</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>82</td> <td>8.73</td> <td>−77.593</td> </tr> <tr> <td scope="row">bromine</td> <td>35</td> <td>Br</td> <td>79</td> <td>50.69</td> <td>−76.068</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>81</td> <td>49.31</td> <td>−77.974</td> </tr> <tr> <td scope="row">krypton</td> <td>36</td> <td>Kr</td> <td>78</td> <td>0.35</td> <td>−74.160</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>80</td> <td>2.28</td> <td>−77.893</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>82</td> <td>11.58</td> <td>−80.589</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>83</td> <td>11.49</td> <td>−79.982</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>84</td> <td>57.00</td> <td>−82.431</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>86</td> <td>17.30</td> <td>−83.266</td> </tr> <tr> <td scope="row">rubidium</td> <td>37</td> <td>Rb</td> <td>85</td> <td>72.17</td> <td>−82.168</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>87</td> <td>27.83</td> <td>−84.595</td> </tr> <tr> <td scope="row">strontium</td> <td>38</td> <td>Sr</td> <td>84</td> <td>0.56</td> <td>−80.644</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>86</td> <td>9.86</td> <td>−84.522</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>87</td> <td>7.00</td> <td>−84.878</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>88</td> <td>82.58</td> <td>−87.920</td> </tr> <tr> <td scope="row">yttrium</td> <td>39</td> <td>Y</td> <td>89</td> <td>100</td> <td>−87.702</td> </tr> <tr> <td scope="row">zirconium</td> <td>40</td> <td>Zr</td> <td>90</td> <td>51.45</td> <td>−88.768</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>91</td> <td>11.22</td> <td>−87.891</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>92</td> <td>17.15</td> <td>−88.455</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>94</td> <td>17.38</td> <td>−87.266</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>96</td> <td>2.80</td> <td>−85.441</td> </tr> <tr> <td scope="row">niobium</td> <td>41</td> <td>Nb</td> <td>93</td> <td>100</td> <td>−87.209</td> </tr> <tr> <td scope="row">molybdenum</td> <td>42</td> <td>Mo</td> <td>92</td> <td>14.84</td> <td>−86.805</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>94</td> <td>9.25</td> <td>−88.410</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>95</td> <td>15.92</td> <td>−87.708</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>96</td> <td>16.68</td> <td>−88.791</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>97</td> <td>9.55</td> <td>−87.541</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>98</td> <td>24.13</td> <td>−88.112</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>100</td> <td>9.63</td> <td>−86.184</td> </tr> <tr> <td scope="row">ruthenium</td> <td>44</td> <td>Ru</td> <td>96</td> <td>5.54</td> <td>−86.072</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>98</td> <td>1.87</td> <td>−88.224</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>99</td> <td>12.76</td> <td>−87.617</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>100</td> <td>12.60</td> <td>−89.219</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>101</td> <td>17.06</td> <td>−87.950</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>102</td> <td>31.55</td> <td>−89.098</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>104</td> <td>18.62</td> <td>−88.091</td> </tr> <tr> <td scope="row">rhodium</td> <td>45</td> <td>Rh</td> <td>103</td> <td>100</td> <td>−88.022</td> </tr> <tr> <td scope="row">palladium</td> <td>46</td> <td>Pd</td> <td>102</td> <td>1.020</td> <td>−87.926</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>104</td> <td>11.14</td> <td>−89.391</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>105</td> <td>22.33</td> <td>−88.414</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>106</td> <td>27.33</td> <td>−89.905</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>108</td> <td>26.46</td> <td>−89.522</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>110</td> <td>11.72</td> <td>−88.350</td> </tr> <tr> <td scope="row">silver</td> <td>47</td> <td>Ag</td> <td>107</td> <td>51.8392</td> <td>−88.405</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>109</td> <td>48.1608</td> <td>−88.720</td> </tr> <tr> <td scope="row">cadmium</td> <td>48</td> <td>Cd</td> <td>106</td> <td>1.25</td> <td>−87.134</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>108</td> <td>0.89</td> <td>−89.253</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>110</td> <td>12.49</td> <td>−90.350</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>111</td> <td>12.80</td> <td>−89.254</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>112</td> <td>24.13</td> <td>−90.581</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>113</td> <td>12.22</td> <td>−89.050</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>114</td> <td>28.73</td> <td>−90.021</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>116</td> <td>7.49</td> <td>−88.720</td> </tr> <tr> <td scope="row">indium</td> <td>49</td> <td>In</td> <td>113</td> <td>4.288</td> <td>−89.366</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>115</td> <td>95.712</td> <td>−89.537</td> </tr> <tr> <td scope="row">tin</td> <td>50</td> <td>Sn</td> <td>112</td> <td>0.973</td> <td>−88.659</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>114</td> <td>0.659</td> <td>−90.558</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>115</td> <td>0.339</td> <td>−90.033</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>116</td> <td>14.536</td> <td>−91.525</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>117</td> <td>7.676</td> <td>−90.398</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>118</td> <td>24.223</td> <td>−91.653</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>119</td> <td>8.585</td> <td>−90.067</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>120</td> <td>32.593</td> <td>−91.103</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>122</td> <td>4.629</td> <td>−89.944</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>124</td> <td>5.789</td> <td>−88.236</td> </tr> <tr> <td scope="row">antimony</td> <td>51</td> <td>Sb</td> <td>121</td> <td>57.213</td> <td>−89.593</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>123</td> <td>42.787</td> <td>−89.222</td> </tr> <tr> <td scope="row">tellurium</td> <td>52</td> <td>Te</td> <td>120</td> <td>0.096</td> <td>−89.405</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>122</td> <td>2.603</td> <td>−90.311</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>123</td> <td>0.908</td> <td>−89.169</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>124</td> <td>4.816</td> <td>−90.523</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>125</td> <td>7.139</td> <td>−89.028</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>126</td> <td>18.952</td> <td>−90.070</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>128</td> <td>31.687</td> <td>−88.994</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>130</td> <td>33.799</td> <td>−87.353</td> </tr> <tr> <td scope="row">iodine</td> <td>53</td> <td>I</td> <td>127</td> <td>100</td> <td>−88.987</td> </tr> <tr> <td scope="row">xenon</td> <td>54</td> <td>Xe</td> <td>124</td> <td>0.08913</td> <td>−87.658</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>126</td> <td>0.08880</td> <td>−89.173</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>128</td> <td>1.91732</td> <td>−89.861</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>129</td> <td>26.43964</td> <td>−89.697</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>130</td> <td>4.08271</td> <td>−89.881</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>131</td> <td>21.17961</td> <td>−88.416</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>132</td> <td>26.89157</td> <td>−89.280</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>134</td> <td>10.44232</td> <td>−88.124</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>136</td> <td>8.86590</td> <td>−86.424</td> </tr> <tr> <td scope="row">cesium</td> <td>55</td> <td>Cs</td> <td>133</td> <td>100</td> <td>−88.076</td> </tr> <tr> <td scope="row">barium</td> <td>56</td> <td>Ba</td> <td>130</td> <td>0.1058</td> <td>−87.271</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>132</td> <td>0.1012</td> <td>−88.440</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>134</td> <td>2.417</td> <td>−88.954</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>135</td> <td>6.592</td> <td>−87.856</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>136</td> <td>7.853</td> <td>−88.892</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>137</td> <td>11.232</td> <td>−87.727</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>138</td> <td>71.699</td> <td>−88.267</td> </tr> <tr> <td scope="row">lanthanum</td> <td>57</td> <td>La</td> <td>138</td> <td>0.09017</td> <td>−86.529</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>139</td> <td>99.91</td> <td>−87.236</td> </tr> <tr> <td scope="row">cerium</td> <td>58</td> <td>Ce</td> <td>136</td> <td>0.186</td> <td>−86.500</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>138</td> <td>0.251</td> <td>−87.574</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>140</td> <td>88.449</td> <td>−88.088</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>142</td> <td>11.114</td> <td>−84.543</td> </tr> <tr> <td scope="row">praseodymium</td> <td>59</td> <td>Pr</td> <td>141</td> <td>100</td> <td>−86.026</td> </tr> <tr> <td scope="row">neodymium</td> <td>60</td> <td>Nd</td> <td>142</td> <td>27.16</td> <td>−85.960</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>143</td> <td>12.18</td> <td>−84.012</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>144</td> <td>23.83</td> <td>−83.758</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>145</td> <td>8.30</td> <td>−81.442</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>146</td> <td>17.17</td> <td>−80.936</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>148</td> <td>5.74</td> <td>−77.418</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>150</td> <td>5.62</td> <td>−73.694</td> </tr> <tr> <td scope="row">samarium</td> <td>62</td> <td>Sm</td> <td>144</td> <td>3.0734</td> <td>−81.976</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>147</td> <td>14.9934</td> <td>−79.276</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>148</td> <td>11.2406</td> <td>−79.347</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>149</td> <td>13.8189</td> <td>−77.147</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>150</td> <td>7.3796</td> <td>−77.061</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>152</td> <td>26.7421</td> <td>−74.773</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>154</td> <td>22.7520</td> <td>−72.465</td> </tr> <tr> <td scope="row">europium</td> <td>63</td> <td>Eu</td> <td>151</td> <td>47.810</td> <td>−74.663</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>153</td> <td>52.190</td> <td>−73.377</td> </tr> <tr> <td scope="row">gadolinium</td> <td>64</td> <td>Gd</td> <td>152</td> <td>0.2029</td> <td>−74.717</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>154</td> <td>2.1809</td> <td>−73.716</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>155</td> <td>14.7998</td> <td>−72.080</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>156</td> <td>20.4664</td> <td>−72.545</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>157</td> <td>15.6518</td> <td>−70.834</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>158</td> <td>24.8347</td> <td>−0.700</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>160</td> <td>21.8635</td> <td>−67.952</td> </tr> <tr> <td scope="row">terbium</td> <td>65</td> <td>Tb</td> <td>159</td> <td>100</td> <td>−69.542</td> </tr> <tr> <td scope="row">dysprosium</td> <td>66</td> <td>Dy</td> <td>156</td> <td>0.056</td> <td>−70.534</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>158</td> <td>0.096</td> <td>−70.417</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>160</td> <td>2.34</td> <td>−69.682</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>161</td> <td>18.91</td> <td>−68.065</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>162</td> <td>25.51</td> <td>−68.190</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>163</td> <td>24.90</td> <td>−66.390</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>164</td> <td>28.19</td> <td>−65.977</td> </tr> <tr> <td scope="row">holmium</td> <td>67</td> <td>Ho</td> <td>165</td> <td>100</td> <td>−64.907</td> </tr> <tr> <td scope="row">erbium</td> <td>68</td> <td>Er</td> <td>162</td> <td>0.137</td> <td>−66.346</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>164</td> <td>1.609</td> <td>−65.953</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>166</td> <td>33.61</td> <td>−64.934</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>167</td> <td>22.93</td> <td>−63.299</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>168</td> <td>26.79</td> <td>−62.999</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>170</td> <td>14.93</td> <td>−60.118</td> </tr> <tr> <td scope="row">thulium</td> <td>69</td> <td>Tm</td> <td>169</td> <td>100</td> <td>−61.282</td> </tr> <tr> <td scope="row">ytterbium</td> <td>70</td> <td>Yb</td> <td>168</td> <td>0.127</td> <td>−61.577</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>170</td> <td>3.04</td> <td>−60.772</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>171</td> <td>14.28</td> <td>−59.315</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>172</td> <td>21.83</td> <td>−59.264</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>173</td> <td>16.13</td> <td>−57.560</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>174</td> <td>31.83</td> <td>−56.953</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>176</td> <td>12.76</td> <td>−53.497</td> </tr> <tr> <td scope="row">lutetium</td> <td>71</td> <td>Lu</td> <td>175</td> <td>97.416</td> <td>−55.174</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>176</td> <td>2.584</td> <td>−53.391</td> </tr> <tr> <td scope="row">hafnium</td> <td>72</td> <td>Hf</td> <td>174</td> <td>0.1620</td> <td>−55.852</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>176</td> <td>5.604</td> <td>−54.584</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>177</td> <td>18.5953</td> <td>−52.890</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>178</td> <td>27.811</td> <td>−52.445</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>179</td> <td>13.6210</td> <td>−50.473</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>180</td> <td>35.0802</td> <td>−49.790</td> </tr> <tr> <td scope="row">tantalum</td> <td>73</td> <td>Ta</td> <td>180</td> <td>0.0123</td> <td>−48.935</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>181</td> <td>99.9877</td> <td>−48.441</td> </tr> <tr> <td scope="row">tungsten</td> <td>74</td> <td>W</td> <td>180</td> <td>0.1198</td> <td>−49.643</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>182</td> <td>26.4985</td> <td>−48.246</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>183</td> <td>14.3136</td> <td>−46.366</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>184</td> <td>30.6422</td> <td>−45.706</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>186</td> <td>28.4259</td> <td>−42.511</td> </tr> <tr> <td scope="row">rhenium</td> <td>75</td> <td>Re</td> <td>185</td> <td>37.398</td> <td>−43.821</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>187</td> <td>62.602</td> <td>−41.218</td> </tr> <tr> <td scope="row">osmium</td> <td>76</td> <td>Os</td> <td>184</td> <td>0.0197</td> <td>−44.254</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>186</td> <td>1.5859</td> <td>−42.999</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>187</td> <td>1.9644</td> <td>−41.220</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>188</td> <td>13.2434</td> <td>−41.138</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>189</td> <td>16.1466</td> <td>−38.988</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>190</td> <td>26.2584</td> <td>−38.708</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>192</td> <td>40.7815</td> <td>−35.882</td> </tr> <tr> <td scope="row">iridium</td> <td>77</td> <td>Ir</td> <td>191</td> <td>37.272</td> <td>−36.709</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>193</td> <td>62.728</td> <td>−34.536</td> </tr> <tr> <td scope="row">platinum</td> <td>78</td> <td>Pt</td> <td>190</td> <td>0.013634</td> <td>−37.325</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>192</td> <td>0.782659</td> <td>−36.296</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>194</td> <td>32.96700</td> <td>−34.779</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>195</td> <td>33.831557</td> <td>−32.812</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>196</td> <td>25.24166</td> <td>−32.663</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>198</td> <td>7.16349</td> <td>−29.923</td> </tr> <tr> <td scope="row">gold</td> <td>79</td> <td>Au</td> <td>197</td> <td>100</td> <td>−31.157</td> </tr> <tr> <td scope="row">mercury</td> <td>80</td> <td>Hg</td> <td>196</td> <td>0.15344</td> <td>−31.843</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>198</td> <td>9.968</td> <td>−30.970</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>199</td> <td>16.873</td> <td>−29.563</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>200</td> <td>23.096</td> <td>−29.520</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>201</td> <td>13.181</td> <td>−27.679</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>202</td> <td>29.863</td> <td>−27.362</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>204</td> <td>6.865</td> <td>−24.707</td> </tr> <tr> <td scope="row">thallium</td> <td>81</td> <td>Tl</td> <td>203</td> <td>29.524</td> <td>−25.775</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>205</td> <td>70.476</td> <td>−23.834</td> </tr> <tr> <td scope="row">lead</td> <td>82</td> <td>Pb</td> <td>204</td> <td>1.4245</td> <td>−25.123</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>206</td> <td>24.1447</td> <td>−23.801</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>207</td> <td>22.0827</td> <td>−22.467</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>208</td> <td>52.3481</td> <td>−21.764</td> </tr> <tr> <td scope="row">bismuth</td> <td>83</td> <td>Bi</td> <td>209</td> <td>100</td> <td>−18.273</td> </tr> <tr> <td scope="row">thorium</td> <td>90</td> <td>Th</td> <td>232</td> <td>100</td> <td>35.444</td> </tr> <tr> <td scope="row">uranium</td> <td>92</td> <td>U</td> <td>234</td> <td>0.00548</td> <td>38.141</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>235</td> <td>0.7200</td> <td>40.914</td> </tr> <tr> <td scope="row"></td> <td></td> <td></td> <td>238</td> <td>99.2745</td> <td>47.304</td> </tr> </tbody> </table></div> </span><p>The specification of <em>Z</em>, <em>A</em>, and the <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/chemical-symbol" class="md-crosslink autoxref">chemical symbol</a> (a one- or two-letter abbreviation of the element’s name, say Sy) in the form <sup><em>A</em></sup><sub><em>Z</em></sub>Sy identifies an isotope adequately for most purposes. Thus, in the standard notation, <sup>1</sup><sub>1</sub>H refers to the simplest isotope of hydrogen and <sup>235</sup><sub>92</sub>U to an isotope of uranium widely used for <a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/technology/nuclear-power" class="md-crosslink autoxref">nuclear power</a> generation and nuclear weapons fabrication. (Authors who do not wish to use symbols sometimes write out the element name and mass number—hydrogen-1 and uranium-235 in the examples above.)</p><span class="marker p5"></span><span class="marker AM5 am-inline"></span><span class="marker MOD5 mod-inline"></span><p>The term <span id="ref496303"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/nuclide" class="md-crosslink"><em>nuclide</em></a> is used to describe particular isotopes, notably in cases where the nuclear rather than the chemical properties of an atom are to be emphasized. The lexicon of isotopes includes three other frequently used terms: <span id="ref496304"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/isotone" class="md-crosslink"><em>isotones</em></a> for isotopes of different elements with the same number of neutrons, <span id="ref496305"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/isobar-nuclear-physics" class="md-crosslink"><em>isobars</em></a> for isotopes of different elements with the same mass number, and <span id="ref496306"></span><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/isomer-nuclear-physics" class="md-crosslink"><em>isomers</em></a> for isotopes identical in all respects except for the total energy content of the nuclei.</p><span class="marker p6"></span><span class="marker AM6 am-inline"></span><span class="marker MOD6 mod-inline"></span></section> <span class="marker end-of-content"></span><span class="marker after-article"></span></div> <aside class="grid-xs-da-300" data-page="1"> <div class="rr-module rr-module-1"> <div class="marketing-RIGHT_RAIL_MODULE marketing-content" data-marketing-id="RIGHT_RAIL_MODULE"><a href="https://web.archive.org/web/20200509141434/https://parents.britannica.com/" target="_blank" rel="noopener"> <img src="https://web.archive.org/web/20200509141434im_/https://safe.britannica.com/safeimages/BFP_marketing_ads_300x90_C.jpg" alt="Learn More!" class="mb-30"/> </a></div></div> <div class="rr-module rr-module-2">  <div class="md-events-box md-content-module-right imars-xml-OTHER_INFO"> <div class="fact-box"> <div class="title">Isotope</div> <div class="subtitle">Quick Facts</div> <div class="fact-box-details md-striped"> <dl data-label="key people"><dt class="fact-list">key people</dt><dd><ul><li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/biography/Francis-William-Aston">Francis William Aston</a></li> <li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/biography/Frederick-Soddy">Frederick Soddy</a></li> <li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/biography/Theodore-William-Richards">Theodore William Richards</a></li></ul></dd></dl> <dl data-label="related topics"><dt class="fact-list">related topics</dt><dd><ul><li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/chemical-element">Chemical element</a></li> <li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/atom">Atom</a></li> <li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/transuranium-element">Transuranium element</a></li> <li><a href="https://web.archive.org/web/20200509141434/https://www.britannica.com/science/isotopic-fractionation">Isotopic fractionation</a></li> <li><a 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