<h2>Compounds</h2>
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<h3>Definition: Compound</h3>
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<p>A compound is a <a data-lesson="chemical-properties-of-the-groups" data-subject="chemistry" data-tutorial="classification-of-matter" href="https://app.ulearngo.com/chemistry/classification-of-matter/chemical-properties-of-the-groups">group</a> of two or more different <a data-lesson="chemical-formulas" data-subject="chemistry" data-tutorial="atoms-molecules-ions" href="https://app.ulearngo.com/chemistry/atoms-molecules-ions/chemical-formulas">atoms</a> that are attracted to each other by relatively strong <a data-lesson="physical-properties-and-intermolecular-forces" data-subject="chemistry" data-tutorial="organic-molecules" href="https://app.ulearngo.com/chemistry/organic-molecules/physical-properties-and-intermolecular-forces">forces</a> or bonds. The atoms are combined in definite proportions.</p>
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<p>Compounds can be divided into <strong>molecular compounds</strong> (molecules), <strong>ionic compounds</strong> (salts) and <strong>metallic compounds</strong> (metals).</p>
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<p><strong>Molecular compounds</strong> form as a result of <a data-lesson="summarizing-covalent-bonding" data-subject="chemistry" data-tutorial="chemical-bonding" href="https://app.ulearngo.com/chemistry/chemical-bonding/summarizing-covalent-bonding">covalent bonding</a> where <a data-lesson="orbital-shapes-and-valence-electrons" data-subject="chemistry" data-tutorial="chemistry-essential-ideas" href="https://app.ulearngo.com/chemistry/chemistry-essential-ideas/orbital-shapes-and-valence-electrons">electrons</a> are shared between non-metal atoms.</p>
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<p><strong>Ionic compounds</strong> form as a result of <a data-lesson="summarizing-ionic-bonding" data-subject="chemistry" data-tutorial="chemical-bonding" href="https://app.ulearngo.com/chemistry/chemical-bonding/summarizing-ionic-bonding">ionic bonding</a> where electrons are transferred from metals to non-metals.</p>
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<p><strong>Metals</strong> are formed as a result of metallic bonding where metal atoms lose their outer electrons to form a lattice of regularly spaced positive ions and a “pool” of delocalised electrons that surround the positive ions.</p>
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<p>The following diagram illustrates how compounds can be subdivided by the type of bonding and the structure:</p>
<p><img alt="a13c140d9ddaf2d855848bdf50bacdc7.png" src="https://data.ulearngo.com/assets/082ea52d-1232-431f-b678-de5df924fa8e"/></p>
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<h2 class="title">Covalent Molecular Structures</h2>
<p>Relatively small molecules are called <strong>covalent molecular structures</strong>. These exist and interact as separate molecules. Oxygen (\(\text{O}_{2}\)), water (\(\text{H}_{2}\text{O}\)), octane (\(\text{C}_{8}\text{H}_{18}\)), sulfur (\(\text{S}_{8}\)) and buckminsterfullerene (\(\text{C}_{60}\), buckyballs) are all examples of covalent molecular structures.</p>
<div class="wp-caption alignnone" style="width: 320px"><img alt="buckminsterfullerene" height="320" src="https://data.ulearngo.com/assets/fdc1c0ee-db84-4e47-8b29-d9aabc44e3c7" width="320"/><p class="wp-caption-text">Example of covalent molecular structures: buckminsterfullerene</p></div> <div class="wp-caption alignnone" style="width: 320px"><img alt="sulfur" height="234" src="https://data.ulearngo.com/assets/7d7e0d72-5f17-4fcd-9b2d-7380c24ec9f1" width="320"/><p class="wp-caption-text">Example of covalent molecular structures: sulfur</p></div>
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<h2 class="title">Network Structures</h2>
<p>Compounds that exist as giant repeating lattice structures are called network structures. Examples include <strong>covalent molecules</strong> such as diamond, graphite and silica. <strong>Ionic substances</strong> are also network structures, for example a sodium chloride crystal is a huge lattice of repeating <a data-lesson="ideal-gas-laws" data-subject="chemistry" data-tutorial="states-of-matter" href="https://app.ulearngo.com/chemistry/states-of-matter/ideal-gas-laws">units</a> made of sodium and chloride ions. All substances formed as a result of ionic bonding are network structures. <strong>Metals</strong> exist as large continuous lattice structures and are also classified as network structures. For example copper, zinc and <a data-lesson="isolation-of-iron" data-subject="chemistry" data-tutorial="transition-metals" href="https://app.ulearngo.com/chemistry/transition-metals/isolation-of-iron">iron</a> can be seen as a giant crystals and are therefore considered to be network structures.</p>
<div class="wp-caption alignnone" style="width: 320px"><img alt="" height="320" src="https://data.ulearngo.com/assets/780da909-b33a-403d-9f38-c7f34b04d336" width="320"/><p class="wp-caption-text">Example of network structures: covalent network</p></div> <div class="wp-caption alignnone" style="width: 320px"><img alt="" height="259" src="https://data.ulearngo.com/assets/564eeb56-9d6d-4bbd-a67e-76de89557bd5" width="320"/><p class="wp-caption-text">Example of network structures: ionic network</p></div> <div class="wp-caption alignnone" style="width: 320px"><img alt="" height="320" src="https://data.ulearngo.com/assets/2971b932-bc0c-4c04-87d7-d11d2123eedc" width="320"/><p class="wp-caption-text">Example of network structures: metallic network</p></div>
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Defining Compounds

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

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.


Defining Compounds

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