Diatomic elements are elements that form diatomic molecules by combining two of their atoms together. The diatomic elements are gases in their natural states and include hydrogen, nitrogen, oxygen, fluorine, chlorine, iodine and bromine.
Diatomic molecules formed of diatomic elements are linear, since the best way to connect two points is with a straight line. Though the two atoms in a diatomic molecule are sharing electrons, the positive charge of the nuclei causes the atoms to repel each other, which gives the bond of diatomic elements a distinguishing vibration that can be seen under scientific observation.
Around 99 percent of Earth's atmosphere consists of the diatomic molecules nitrogen, or N2, and oxygen, or O2. Nitrogen makes up about 78 percent of the atmosphere, and oxygen makes up another 21 percent. Hydrogen, in the form of H2, is the most abundant element in the universe.
A good mnemonic to use for remembering the seven diatomic elements is "Have No Fear Of Ice Cold Beer." The first letters of each word corresponds to the atomic symbols of the seven elements: H for hydrogen, N for Nitrogen, F for fluorine, O for oxygen, I for iodine, Cl for chlorine and Br for bromine.