How do halogens form diatomic molecules?

Halogens form diatomic molecules by sharing a pair of electrons between two atoms, creating a single covalent bond.

Halogens are elements found in Group 17 of the periodic table and include fluorine, chlorine, bromine, iodine, and astatine. They are known for their high reactivity, which is due to their electron configuration. Each halogen atom has seven electrons in its outermost shell and needs one more to achieve a stable, full outer shell, similar to the noble gases. This makes them highly reactive and eager to form bonds with other elements or with themselves.

When two halogen atoms come together, they can share a pair of electrons, one from each atom, to form a single covalent bond. This process is known as covalent bonding. The shared pair of electrons orbits the nuclei of both atoms, effectively 'gluing' them together to form a molecule. In the case of halogens, this results in the formation of a diatomic molecule, meaning a molecule composed of two atoms of the same element. For example, two fluorine atoms can bond together to form a molecule of F2, or diatomic fluorine.

This electron sharing allows each halogen atom to achieve a full outer shell of eight electrons, satisfying the octet rule. The octet rule states that atoms are most stable when their outermost shell is full, typically with eight electrons. By sharing a pair of electrons, each halogen atom in the molecule effectively has eight electrons in its outer shell, even though one of those electrons is shared with the other atom.

In summary, halogens form diatomic molecules through covalent bonding, where a pair of electrons is shared between two atoms. This allows each atom to achieve a stable, full outer shell of electrons, satisfying the octet rule and resulting in a highly stable diatomic molecule.