<h2>Spectroscopic Electron Configuration Notation</h2>
<p>A special type of notation is used to show an atom's electron configuration. The notation describes the <a data-lesson="energy" data-subject="chemistry" data-tutorial="thermochemistry" href="https://app.ulearngo.com/chemistry/thermochemistry/energy">energy</a> levels, <a data-lesson="hybrid-atomic-orbitals" data-subject="chemistry" data-tutorial="covalent-bonding-continued" href="https://app.ulearngo.com/chemistry/covalent-bonding-continued/hybrid-atomic-orbitals">orbitals</a> and the number of electrons in each. For example, the electron configuration of lithium is \(1\text{s}^{2}2\text{s}^{1}\). The number and letter describe the energy level and orbital and the number above the orbital shows how many electrons are in that orbital.</p>
<p>Aufbau diagrams for the <a data-lesson="elements" data-subject="chemistry" data-tutorial="classification-of-matter" href="https://app.ulearngo.com/chemistry/classification-of-matter/elements">elements</a> fluorine and argon are shown in figure 1 and figure 2 below respectively. Using spectroscopic notation, the electron configuration of fluorine is \(1\text{s}^{2}2\text{s}^{2}2\text{p}^{5}\) and the electron configuration of argon is \(1\text{s}^{2}2\text{s}^{2}2\text{p}^{5}3\text{s}^{2}3\text{p}^{6}\).</p>
<div class="wp-caption alignnone" style="width: 654px"><img alt="128bf29f0a6b282fa5ea16f1ac1306ce.png" height="860" src="https://data.ulearngo.com/assets/46a77443-23c7-4381-92e8-519db319ffed" width="654"/><p class="wp-caption-text">Figure 1: An Aufbau diagram showing the electron configuration of fluorine</p></div> <div class="wp-caption alignnone" style="width: 654px"><img alt="d2e8b5bcc1ef3ed375d7b4cea5ecd851.png" height="860" src="https://data.ulearngo.com/assets/990f4045-5403-45e2-87d0-c542c6a4a679" width="654"/><p class="wp-caption-text">Figure 2: An Aufbau diagram showing the electron configuration of argon</p></div>
<div class="ns-school-defn2">
<h3>Tip:</h3>
<p>The spectroscopic electron configuration can be written in shorter form. This form is written as [noble gas]electrons, where the noble <a data-lesson="non-ideal-gas-behavior" data-subject="chemistry" data-tutorial="gases" href="https://app.ulearngo.com/chemistry/gases/non-ideal-gas-behavior">gas</a> is the nearest one that occurs before the element. For example, magnesium can be represented as \([\text{Ne}]3\text{s}^{2}\) and carbon as \([\text{H}]2\text{s}^{2}2\text{p}^{2}\). This is known as the condensed electron configuration.</p>
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<div class="ns-school-emp">
<h2>Example: Aufbau Diagrams and Spectroscopic Electron Configuration</h2>
<div class="ns-school-defn">
<h3>Question</h3>
<div>
<p>Give the electron configuration for <a data-lesson="occurrence-preparation-and-properties-of-nitrogen" data-subject="chemistry" data-tutorial="metals-metalloids-nonmetals" href="https://app.ulearngo.com/chemistry/metals-metalloids-nonmetals/occurrence-preparation-and-properties-of-nitrogen">nitrogen</a> (N) and draw an Aufbau diagram.</p>
</div>
<div>
<h3>Step 1: Give the number of electrons</h3>
<p>Nitrogen has seven electrons.</p>
</div>
<div>
<h3>Step 2: Place two electrons in the 1s orbital</h3>
<p>We start by placing two electrons in the 1s orbital: \(1\text{s}^{2}\).</p>
<img alt="b2722eac3a7e565133225858c33506a3.png" src="https://data.ulearngo.com/assets/608be3d4-9f91-4f7e-9120-a496ec958a4c"/>
<p>Now we have five electrons left to place in orbitals.</p>
</div>
<div>
<h3>Step 3: Place two electrons in the 2s orbital</h3>
<p>We put two electrons in the 2s orbital: \(2\text{s}^{2}\).</p>
<img alt="e3c060a1cccef5e77441d0a384f83295.png" src="https://data.ulearngo.com/assets/d8784a8c-ed39-4a53-9109-220b3a8e66ac"/>
<p>There are now three electrons to place in orbitals.</p>
</div>
<div>
<h3>Step 4: Place three electrons in the 2p orbital</h3>
<p>We place three electrons in the 2p orbital: \(2\text{p}^{3}\).</p>
<img alt="61f119736655ac711ca43b190bdb368e.png" src="https://data.ulearngo.com/assets/14bab0d7-af78-413e-8584-4d50f51fe5c9"/></div>
<div>
<h3>Step 5: Write the final answer</h3>
<p>The electron configuration is: \(1\text{s}^{2}2\text{s}^{2}2\text{p}^{3}\). The Aufbau diagram is given in the step above.</p>
</div>
</div>
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<section>
<h2 class="title">Aufbau Diagrams for Ions</h2>
<p>When a neutral atom loses an electron it becomes positively charged and we call it a cation. For example, <a data-lesson="redox-reactions" data-subject="chemistry" data-tutorial="reactions-in-aqueous-solution" href="https://app.ulearngo.com/chemistry/reactions-in-aqueous-solution/redox-reactions">sodium</a> will lose one electron and become \(\text{Na}^{+}\) or calcium will lose two electrons and become \(\text{Ca}^{2+}\). In each of these cases, the outermost electron(s) will be lost.</p>
<p>When a neutral atom gains an electron it becomes negatively charged and we call it an anion. For example chlorine will gain one electron and become \(\text{Cl}^{-}\) or oxygen will gain two electrons and become \(\text{O}^{2-}\).</p>
<p>Aufbau diagrams and electron configurations can be done for cations and <a data-lesson="electronic-structures-of-anions" data-subject="chemistry" data-tutorial="chemical-bonding" href="https://app.ulearngo.com/chemistry/chemical-bonding/electronic-structures-of-anions">anions</a> as well. The following worked example will show you how.</p>
<div class="ns-school-emp">
<h2>Example: Aufbau Diagram for an Ion</h2>
<div class="ns-school-defn">
<h3>Question</h3>
<div>
<p>Give the electron configuration for (\(\text{O}^{2-}\)) and draw an Aufbau diagram.</p>
</div>
<div>
<h3>Step 1: Give the number of electrons</h3>
<p>Oxygen has eight electrons. The oxygen anion has gained two electrons and so the total number of electrons is ten.</p>
</div>
<div>
<h3>Step 2: Place two electrons in the 1s orbital</h3>
<p>We start by placing two electrons in the 1s orbital: \(1\text{s}^{2}\).</p>
<img alt="b2722eac3a7e565133225858c33506a3.png" src="https://data.ulearngo.com/assets/8e09e4b2-9be8-40b1-a60e-09b9c78d0372"/>
<p>Now we have eight electrons left to place in orbitals.</p>
</div>
<div>
<h3>Step 3: Place two electrons in the 2s orbital</h3>
<p>We put two electrons in the 2s orbital: \(2\text{s}^{2}\).</p>
<img alt="e3c060a1cccef5e77441d0a384f83295.png" src="https://data.ulearngo.com/assets/c07280d4-1a95-4e7e-a5c7-714c2418b3ed"/>
<p>There are now six electrons to place in orbitals.</p>
</div>
<div>
<h3>Step 4: Place six electrons in the 2p orbital</h3>
<p>We place six electrons in the 2p orbital: \(2\text{p}^{6}\).</p>
</div>
<div>
<h3>Step 5: Write the final answer</h3>
<p>The electron configuration is: \(1\text{s}^{2}2\text{s}^{2}2\text{p}^{6}\). The Aufbau diagram is:</p>
<img alt="7479e1aabe12ae0948602cbec9656143.png" src="https://data.ulearngo.com/assets/ecd6b99e-f987-436c-be19-fa507b6dd0af"/></div>
</div>
</div>
<div class="ns-school-defn2">
<h3>Did You Know?</h3>
<p>When we draw the orbitals we draw a shape that has a boundary (i.e. a closed shape). This represents the distance from <a data-lesson="the-nucleus-2" data-subject="chemistry" data-tutorial="chemistry-essential-ideas" href="https://app.ulearngo.com/chemistry/chemistry-essential-ideas/the-nucleus-2">the nucleus</a> in which we are \(\text{95}\%\) sure that we will find the electrons. In reality the electrons of an atom could be found any distance away from the nucleus.</p>
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</section>
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Spectroscopic Electron Configuration

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. 

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Explore the essential ideas in chemistry, including the scientific method, laboratory skills and safety, states of matter, measurement uncertainty, models of the atom, electronic configurations, and more.


Spectroscopic Electron Configuration

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