What is an Ionic Bond?
Atoms bond to one another because they are seeking to stabilize their electron configuration, typically by filling their outermost shell with eight electrons. To accomplish this, some atoms share electrons while others take or give electrons.
Ionic bonds occur when one atom gives up an electron pair to another atom in order to leave them both with a more stable electron configuration. Usually this kind of bond forms between a metal and a nonmetal, with the metal giving up an electron and the nonmetal receiving an electron.
For an ionic bond to work, the two atoms involved must have very different electronegativity value. Electronegativity is a measure of how strongly a particular atom attracts electrons, or how badly it “wants” to fill its outer shell. Atoms with low electronegativity easily give up electrons, while atoms with high electronegativity easily take electrons. Typically two atoms must have a electronegativity difference of greater than 1.7 to form an ionic bond.
When the two atoms exchange electrons, one becomes a positively charged ion and the other becomes a negatively charged ion. These oppositely charged ions are then attracted to each other, like magnets, which is what forms the bond.
An example of an ionic bond that you probably use in your everyday life is table salt, also known as sodium chloride. The chlorine atom only needs one electron to fill its outermost shell with a full eight electrons, so it helps itself to the single electron orbiting in the sodium’s outermost shell. This leaves both atoms with stable electron configurations. It also leaves the sodium atom positively charged and the chlorine atom negatively charged.
Ionic bonds and covalent bonds, which form when two atoms share electrons, have different properties due to the way they form. For example, ionic bonds have a higher bond dissociation energy, which means it takes more energy to break them. Molecules and compounds formed by ionic bonds also tend to have higher melting and boiling points and are overall better at conducting electricity. Most ionic bonds also are highly polar due to their “opposites attract” nature.
In contrast, covalent bonds tend to have a lower melting and boiling point, be less polar, and are usually liquid or gas at room temperature.
Tes.com. (2019). Lessons - Ionic Bonding [digital art]. Retrieved from https://www.tes.com/lessons/mK7KV_osjT-6vQ/ionic-bonding