<h2>What is a chemical symbol?</h2>
<p>A <strong>chemical symbol</strong> is an abbreviation that we use to indicate an element or an atom of an element. For example, the symbol for mercury is <em>Hg</em> (<a href="#attachment_96181">see image below</a>). We use the same symbol to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain).</p>
<div class="wp-caption alignnone" id="attachment_96181" style="width: 600px"><a href="https://data.ulearngo.com/assets/14fbba32-0aea-45fa-9e25-6b6272020567"><img alt="mercury-symbol" class="size-full wp-image-96181" height="480" src="https://data.ulearngo.com/assets/14fbba32-0aea-45fa-9e25-6b6272020567" width="600"/></a><p class="wp-caption-text">The symbol Hg represents the element mercury regardless of the amount; it could represent one atom of mercury or a large amount of mercury. Image credit: OpenStax, Chemistry</p></div>
<p>The symbols for several common elements and their atoms are listed in the table below. Some symbols are derived from the common name of the element; others are abbreviations of the name in another language. Most symbols have one or two letters, but three-letter symbols have been used to describe some elements that have atomic numbers greater than 112.</p>
<p>To avoid confusion with other notations, only the first letter of a symbol is capitalized. For example, Co is the symbol for the element cobalt, but CO is the notation for the compound carbon monoxide, which contains atoms of the elements carbon (C) and oxygen (O). All known elements and their symbols are in the <a href="https://app.ulearngo.com/lesson/extensive-intensive-properties">periodic table</a> which we will discuss later.</p>
<table class="span-all" id="fs-idm36686800" summary="This table has two columns labeled element and symbol. The first letter of the symbol is always an uppercase letter while the second letter of the symbol is always a lowercase letter. Aluminum has the symbol A L. Bromine has the symbol B R, calcium has the symbol C A, carbon has the symbol C, chlorine has the symbol C L, chromium has the symbol C R, cobalt has the symbol C O, copper has the symbol C U, from cuprum, fluorine has the symbol F, gold has the symbol A U, from aurum, helium has the symbol H E, hydrogen has the symbol H, iodine has the symbol I, iron has the symbol F E, from ferrum, lead has the symbol P B, from plumbum, magnesium has the symbol M G, mercury has the symbol H G from hydrargyrum, nitrogen has the symbol N, oxygen has the symbol O, potassium has the symbol K, from kalium, silicon has the symbol S I, silver has the symbol A G, from argentum, sodium has the symbol N A from natrium, sulfur has the symbol S, tin has the symbol S N from stannum, and zinc has the symbol Z N.">
<thead>
<tr>
<th colspan="4" data-align="center" scope="col">
<h3>Some Common Elements and Their Symbols</h3>
</th>
</tr>
<tr valign="top">
<th data-align="left" scope="col">Element</th>
<th data-align="left" scope="col">Symbol</th>
<th data-align="left" scope="col">Element</th>
<th data-align="left" scope="col">Symbol</th>
</tr>
</thead>
<tbody>
<tr valign="top">
<td data-align="left">aluminum</td>
<td data-align="left">Al</td>
<td data-align="left">iron</td>
<td data-align="left">Fe (from <em data-effect="italics">ferrum</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">bromine</td>
<td data-align="left">Br</td>
<td data-align="left">lead</td>
<td data-align="left">Pb (from <em data-effect="italics">plumbum</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">calcium</td>
<td data-align="left">Ca</td>
<td data-align="left">magnesium</td>
<td data-align="left">Mg</td>
</tr>
<tr valign="top">
<td data-align="left">carbon</td>
<td data-align="left">C</td>
<td data-align="left">mercury</td>
<td data-align="left">Hg (from <em data-effect="italics">hydrargyrum</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">chlorine</td>
<td data-align="left">Cl</td>
<td data-align="left">nitrogen</td>
<td data-align="left">N</td>
</tr>
<tr valign="top">
<td data-align="left">chromium</td>
<td data-align="left">Cr</td>
<td data-align="left">oxygen</td>
<td data-align="left">O</td>
</tr>
<tr valign="top">
<td data-align="left">cobalt</td>
<td data-align="left">Co</td>
<td data-align="left">potassium</td>
<td data-align="left">K (from <em data-effect="italics">kalium</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">copper</td>
<td data-align="left">Cu (from <em data-effect="italics">cuprum</em>)</td>
<td data-align="left">silicon</td>
<td data-align="left">Si</td>
</tr>
<tr valign="top">
<td data-align="left">fluorine</td>
<td data-align="left">F</td>
<td data-align="left">silver</td>
<td data-align="left">Ag (from<em data-effect="italics"> argentum</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">gold</td>
<td data-align="left">Au (from <em data-effect="italics">aurum</em>)</td>
<td data-align="left">sodium</td>
<td data-align="left">Na (from <em data-effect="italics">natrium</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">helium</td>
<td data-align="left">He</td>
<td data-align="left">sulfur</td>
<td data-align="left">S</td>
</tr>
<tr valign="top">
<td data-align="left">hydrogen</td>
<td data-align="left">H</td>
<td data-align="left">tin</td>
<td data-align="left">Sn (from <em data-effect="italics">stannum</em>)</td>
</tr>
<tr valign="top">
<td data-align="left">iodine</td>
<td data-align="left">I</td>
<td data-align="left">zinc</td>
<td data-align="left">Zn</td>
</tr>
</tbody>
</table>
<p>Traditionally, the discoverer (or discoverers) of a new element names the element. However, until the name is recognized by the International Union of Pure and Applied Chemistry (<a href="https://iupac.org/">IUPAC</a>), the recommended name of the new element is based on the Latin word(s) for its atomic number.</p>
<p>For example, element 106 was called unnilhexium (Unh), element 107 was called unnilseptium (Uns), and element 108 was called unniloctium (Uno) for several years. These elements are now named after scientists (or occasionally locations); for example, element 106 is now known as <em data-effect="italics">seaborgium</em> (Sg) in honor of Glenn Seaborg, a Nobel Prize winner who was active in the discovery of several heavy elements.</p>
<h2>Isotopes</h2>
<p>The symbol for a specific isotope of any element is written by placing the mass number as a superscript to the left of the element symbol (<a href="#attachment_96182">see image below</a>). The atomic number is sometimes written as a subscript preceding the symbol, but since this number defines the element’s identity, as does its symbol, it is often omitted.</p>
<p>For example, magnesium exists as a <a data-lesson="mixtures" data-subject="chemistry" data-tutorial="classification-of-matter" href="https://app.ulearngo.com/chemistry/classification-of-matter/mixtures">mixture</a> of three isotopes, each with an atomic number of 12 and with mass numbers of 24, 25, and 26, respectively. These <a data-lesson="isotopes" data-subject="chemistry" data-tutorial="chemistry-essential-ideas" href="https://app.ulearngo.com/chemistry/chemistry-essential-ideas/isotopes">isotopes</a> can be identified as <sup>24</sup>Mg, <sup>25</sup>Mg, and <sup>26</sup>Mg. These isotope symbols are read as “element, mass number” and can be symbolized consistent with this reading. For instance, <sup>24</sup>Mg is read as “magnesium 24,” and can be written as “magnesium-24” or “Mg-24.” <sup>25</sup>Mg is read as “magnesium 25,” and can be written as “magnesium-25” or “Mg-25.” All magnesium atoms have 12 protons in their nucleus. They differ only because a <sup>24</sup>Mg atom has 12 neutrons in its nucleus, a <sup>25</sup>Mg atom has 13 neutrons, and a <sup>26</sup>Mg has 14 neutrons.</p>
<div class="wp-caption alignnone" id="attachment_96182" style="width: 650px"><a href="https://data.ulearngo.com/assets/204d95a4-265f-4726-988b-871781273732"><img alt="atom-symbol" class="size-full wp-image-96182" height="144" src="https://data.ulearngo.com/assets/204d95a4-265f-4726-988b-871781273732" width="650"/></a><p class="wp-caption-text">The symbol for an atom indicates the element via its usual two-letter symbol, the mass number as a left superscript, the atomic number as a left subscript (sometimes omitted), and the charge as a right superscript. Image credit: OpenStax, Chemistry</p></div>
<p>Information about the naturally occurring isotopes of elements with atomic numbers 1 through 10 is given in the table below. Note that in addition to standard names and symbols, the isotopes of hydrogen are often referred to using common names and accompanying symbols. Hydrogen-2, symbolized <sup>2</sup>H, is also called deuterium and sometimes symbolized D. Hydrogen-3, symbolized <sup>3</sup>H, is also called tritium and sometimes symbolized T.</p>
<table class="span-all" id="fs-idm87646592" summary="This table has seven columns labeled element, symbol, atomic number, number of protons, number of neutrons, mass in A M U, and percent natural abundance. The symbols for each element each show the mass number in the upper left and the atomic number in the lower left. Therefore hydrogen left superscript 1, left subscript 1, or protium, has a mass number of 1 and an atomic number of 1. Protium has one proton, 0 neutrons, a mass of 1.0078 and a natural abundance percentage of 99.985. Hydrogen left superscript 2, left subscript 1, or deuterium, has an atomic number of 1, 1 proton, 1 neutron, a mass of 2.0141 and a natural abundance percentage of 0.015. Hydrogen left superscript 3, left subscript 1, or tritium, has an atomic number of 11 protons, 2 neutrons, and a mass of 3.01605. No natural abundance percentage is given. Helium left superscript 3, left subscript 2 has an atomic number of 2, 2 protons, 1 neutron, a mass of 3.01603, and a natural abundance percentage of 0.00013. Helium left superscript 4, left subscript 2 has an atomic number of 2, 2 protons, 2 neutrons, a mass of 4.0026 and a natural abundance percentage of 100. Lithium left superscript 6, left subscript 3 has an atomic number of 3, 3 protons, 3 neutrons, a mass of 6.0151, and a natural abundance percentage of 7.42. Lithium left superscript 7, left subscript 3 has an atomic number of 3, 3 protons, 4 neutrons, a mass of 7.0160, and a natural abundance percentage of 92.8. Beryllium left superscript 9, left subscript 4 has an atomic number of 4, 4 protons, 5 neutrons, a mass of 9.0122, and a natural abundance percentage of 100. Boron left superscript 10, left subscript 5 has an atomic number of 5, 5 protons, 5 neutrons and a natural abundance percentage of 19.9. Boron left superscript 11, left subscript 5 has an atomic number of 5, 5 protons, 6 neutrons, a mass of 11.0093 and a natural abundance of 80.1. Carbon left superscript 12, left subscript 6 has an atomic number of 6, 6 protons, 6 neutrons, a mass of 12, and a natural abundance percentage of 98.89. Carbon left superscript 13, left subscript 6 has an atomic number of 6, 6 protons, 7 neutrons, a mass of 13.0033, and a natural abundance percentage of 1.11. Carbon left superscript 14, left subscript 6 has an atomic number of 6, 6 protons, 8 neutrons, and a mass of 14.0032. Its natural abundance percentage is not reported. Nitrogen left superscript 14, left subscript 7 has an atomic number of 7, 7 protons, 7 neutrons, a mass of 14.0031, and a natural abundance percentage of 99.63. Nitrogen left superscript 15, left subscript 7 has an atomic number of 7, 7 protons, 8 neutrons, a mass of 15.0001, and a natural abundance percentage of 0.37. Oxygen left superscript 16, left subscript 8 has an atomic number of 8, 8 protons, 8 neutrons, a mass of 15.9949, and a natural abundance percentage of 99.759. Oxygen left superscript 17, left subscript 8 has an atomic number of 8, 8 protons, 9 neutrons, a mass of 16.9991, and a natural abundance percentage of 0.037. Oxygen left superscript 18, left subscript 8 has an atomic number of 8, 8 protons, 10 neutrons, a mass of 17.9992, and a natural abundance percentage of 0.204. Fluorine left superscript 19, left subscript 9 has an atomic number of 9, 9 protons, 10 neutrons, a mass of 18.9984, and a natural abundance percentage of 100. Neon left superscript 20, left subscript 10 has an atomic number of 10, 10 protons, 10 neutrons, a mass of 19.9924, and a natural abundance percentage of 90.92. Neon left superscript 21, left subscript 10 has an atomic number of 10, 10 protons, 11 neutrons, a mass of 20.994, and a natural abundance percentage of 0.257. Neon left superscript 22, left subscript 10 has an atomic number of 10, 10 protons, 12 neutrons, a mass of 21.9914, and a natural abundance percentage of 8.82.">
<thead>
<tr>
<th colspan="7" data-align="center" scope="col">
<h3>Nuclear Compositions of Atoms of the Very Light Elements</h3>
</th>
</tr>
<tr valign="top">
<th data-align="left" scope="col">Element</th>
<th data-align="left" scope="col">Symbol</th>
<th data-align="left" scope="col">Atomic Number</th>
<th data-align="left" scope="col">Number of Protons</th>
<th data-align="left" scope="col">Number of Neutrons</th>
<th data-align="left" scope="col">Mass (amu)</th>
<th data-align="left" scope="col">% Natural Abundance</th>
</tr>
</thead>
<tbody>
<tr valign="middle">
<td data-align="left" rowspan="3">hydrogen</td>
<td data-align="center">
<p>\(^{1}_{1}\text{H}\)<br/>
 (protium)</p>
</td>
<td data-align="center">1</td>
<td data-align="center">1</td>
<td data-align="center">0</td>
<td data-align="center">1.0078</td>
<td data-align="center">99.989</td>
</tr>
<tr valign="top">
<td data-align="center">
<div data-type="newline">\(^{2}_{1}\text{H}\)</div>

(deuterium)</td>
<td data-align="center">1</td>
<td data-align="center">1</td>
<td data-align="center">1</td>
<td data-align="center">2.0141</td>
<td data-align="center">0.0115</td>
</tr>
<tr valign="top">
<td data-align="center">
<div data-type="newline">\(^{3}_{1}\text{H}\)</div>
<div data-type="newline"><span style="font-family: inherit; font-size: inherit;">(tritium)</span></div>
</td>
<td data-align="center">1</td>
<td data-align="center">1</td>
<td data-align="center">2</td>
<td data-align="center">3.01605</td>
<td data-align="center">— (trace)</td>
</tr>
<tr valign="middle">
<td data-align="center" rowspan="2">helium</td>
<td data-align="center">\(^{3}_{2}\text{He}\)</td>
<td data-align="center">2</td>
<td data-align="center">2</td>
<td data-align="center">1</td>
<td data-align="center">3.01603</td>
<td data-align="center">0.00013</td>
</tr>
<tr valign="top">
<td data-align="center">\(^{4}_{2}\text{He}\)</td>
<td data-align="center">2</td>
<td data-align="center">2</td>
<td data-align="center">2</td>
<td data-align="center">4.0026</td>
<td data-align="center">100</td>
</tr>
<tr valign="middle">
<td data-align="center" rowspan="2">lithium</td>
<td data-align="center">\(^{6}_{3}\text{Li}\)</td>
<td data-align="center">3</td>
<td data-align="center">3</td>
<td data-align="center">3</td>
<td data-align="center">6.0151</td>
<td data-align="center">7.59</td>
</tr>
<tr valign="top">
<td data-align="center">\(^{7}_{3}\text{Li}\)</td>
<td data-align="center">3</td>
<td data-align="center">3</td>
<td data-align="center">4</td>
<td data-align="center">7.0160</td>
<td data-align="center">92.41</td>
</tr>
<tr valign="top">
<td data-align="left">beryllium</td>
<td data-align="center">\(^{9}_{4}\text{Be}\)</td>
<td data-align="center">4</td>
<td data-align="center">4</td>
<td data-align="center">5</td>
<td data-align="center">9.0122</td>
<td data-align="center">100</td>
</tr>
<tr valign="middle">
<td data-align="left" rowspan="2">boron</td>
<td data-align="center">\(^{10}_{5}\text{B}\)</td>
<td data-align="center">5</td>
<td data-align="center">5</td>
<td data-align="center">5</td>
<td data-align="center">10.0129</td>
<td data-align="center">19.9</td>
</tr>
<tr valign="top">
<td data-align="center">\(^{11}_{5}\text{B}\)</td>
<td data-align="center">5</td>
<td data-align="center">5</td>
<td data-align="center">6</td>
<td data-align="center">11.0093</td>
<td data-align="center">80.1</td>
</tr>
<tr valign="middle">
<td data-align="left" rowspan="3">carbon</td>
<td data-align="center">\(^{12}_{6}\text{C}\)</td>
<td data-align="center">6</td>
<td data-align="center">6</td>
<td data-align="center">6</td>
<td data-align="center">12.0000</td>
<td data-align="center">98.89</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{13}_{6}\text{C}\)</td>
<td data-align="center">6</td>
<td data-align="center">6</td>
<td data-align="center">7</td>
<td data-align="center">13.0034</td>
<td data-align="center">1.11</td>
</tr>
<tr valign="top">
<td data-align="center">\(^{14}_{6}\text{C}\)</td>
<td data-align="center">6</td>
<td data-align="center">6</td>
<td data-align="center">8</td>
<td data-align="center">14.0032</td>
<td data-align="center">— (trace)</td>
</tr>
<tr valign="middle">
<td data-align="center" rowspan="2">nitrogen</td>
<td data-align="center">\(^{14}_{7}\text{N}\)</td>
<td data-align="center">7</td>
<td data-align="center">7</td>
<td data-align="center">7</td>
<td data-align="center">14.0031</td>
<td data-align="center">99.63</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{15}_{7}\text{N}\)</td>
<td data-align="center">7</td>
<td data-align="center">7</td>
<td data-align="center">8</td>
<td data-align="center">15.0001</td>
<td data-align="center">0.37</td>
</tr>
<tr valign="middle">
<td data-align="center" rowspan="3">oxygen</td>
<td data-align="center">\(^{16}_{8}\text{O}\)</td>
<td data-align="center">8</td>
<td data-align="center">8</td>
<td data-align="center">8</td>
<td data-align="center">15.9949</td>
<td data-align="center">99.757</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{17}_{8}\text{O}\)</td>
<td data-align="center">8</td>
<td data-align="center">8</td>
<td data-align="center">9</td>
<td data-align="center">16.9991</td>
<td data-align="center">0.038</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{18}_{8}\text{O}\)</td>
<td data-align="center">8</td>
<td data-align="center">8</td>
<td data-align="center">10</td>
<td data-align="center">17.9992</td>
<td data-align="center">0.205</td>
</tr>
<tr valign="middle">
<td data-align="left">fluorine</td>
<td data-align="center">\(^{19}_{9}\text{F}\)</td>
<td data-align="center">9</td>
<td data-align="center">9</td>
<td data-align="center">10</td>
<td data-align="center">18.9984</td>
<td data-align="center">100</td>
</tr>
<tr valign="middle">
<td data-align="left" rowspan="3">neon</td>
<td data-align="center">\(^{20}_{10}\text{Ne}\)</td>
<td data-align="center">10</td>
<td data-align="center">10</td>
<td data-align="center">10</td>
<td data-align="center">19.9924</td>
<td data-align="center">90.48</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{21}_{10}\text{Ne}\)</td>
<td data-align="center">10</td>
<td data-align="center">10</td>
<td data-align="center">11</td>
<td data-align="center">20.9938</td>
<td data-align="center">0.27</td>
</tr>
<tr valign="middle">
<td data-align="center">\(^{22}_{10}\text{Ne}\)</td>
<td data-align="center">10</td>
<td data-align="center">10</td>
<td data-align="center">12</td>
<td data-align="center">21.9914</td>
<td data-align="center">9.25</td>
</tr>
</tbody>
</table>

Chemistry generally explores the substances of which matter is composed, the investigation of their properties and reactions, and the use of such reactions to form new substances. 

Chemistry

Chemical Symbols and Isotopes

Discover the composition of matter, early ideas in atomic theory, atomic structure and symbolism, the periodic table, and chemical nomenclature in this tutorial on atoms, molecules, and ions.


Chemical Symbols and Isotopes

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