Author: Vincent Guo
Editors: Jaylen Peng and Misha Wichita
Artist: Emily Hu
Chemical compounds make up our world and contribute to chemistry as the central science. The air we breathe out and the water we drink are all chemical compounds: two or more elements bonded together. Water is formed by two elements, hydrogen and oxygen, while carbon dioxide is formed from carbon and oxygen. There are two types of simple bonds: ionic and covalent, also known as molecular bonds.
Ionic bonds typically occur between a metal element and a nonmetal element. The nonmetal element gives away electrons to the metal element, resulting in neither having valence electrons available for bonding. The ionic compound forms a lattice or crystal-like structure, which explains some of its characteristics. For example, ionic compounds are brittle, hard, and have high boiling and melting points. Furthermore, covalent bonding occurs between two nonmetal elements that share a pair of electrons with each other. One characteristic of covalent bonds is their low boiling and melting points. One difference between the two types of bonds is that ionic compounds are great conductors of electricity as liquids, while covalent bonds are not conductive in any state of matter. Whether a compound is ionic or covalent can be determined by looking at the compound's overall electronegativity, or how much an element wants to gain an electron. Metal elements have low electronegativity because they tend to give away their valence electrons. Nonmetals, on the other hand, have high electronegativity because they tend to gain electrons and have no valence electrons. A compound is ionic if it has a 1.7 or smaller electronegativity difference between the two elements. However, the compound is covalent if a compound has a 1.7 or higher electronegativity difference between the elements.
In addition to molecular bonds, there are metallic bonds, hydrogen bonds, dipole-dipole, and London dispersion forces. Metallic bonding occurs between metal elements and is characterized by electrons freely moving within a metallic bond, making metals good conductors of electricity in any state of matter. Dipole-dipole bonds are formed between two different elements, and one of the elements has a higher electronegativity. Dipole-dipole bonds share one electron, but as there are two different elements, one of the elements will have a higher electronegativity. The element with the stronger electronegativity pulls the shared electron closer to itself than the other element. This causes the element with the higher electronegativity to have a negative charge and the weaker one with a positive charge. London dispersion forces, also known as Van Der Waal forces, can occur between neutral atoms. These forces are weak and only occur when atoms are close to each other. If the distance between the atoms increases, these forces don’t act within the elements. Hydrogen bonds occur between hydrogen and three other elements: fluorine, oxygen, and nitrogen.
Elements may form compounds in an attempt to become more stable. They become more stable when combined into compounds because energy is released during the formation process. Conversely, when compounds are broken down, energy is absorbed. All in all, elements are more stable when they have less energy, which is why they tend to form compounds.
Citations:
“Dipole-Dipole, London Dispersion and Hydrogen Bonding Interactions.” Chemistry Steps,
22 Oct. 2020, www.chemistrysteps.com/dipole-dipole-london-dispersion-and-
“Chemical Bonds: Definition, Types, and Examples.” Chemistry Learner,
Stewart, Ken. “Ionic Compound | Chemistry.” Encyclopedia Britannica, Encyclopedia
Britannica, 27 Feb. 2023, www.britannica.com/science/ionic-compound.
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