Here's why:

* Valence Electrons: Iodine has 7 valence electrons in its outermost shell.

* Octet Rule: To achieve a stable electron configuration, iodine needs to gain one more electron to complete its octet.

* Covalent Bonding: Iodine achieves this by sharing one electron with another atom, forming a single covalent bond.

While iodine can sometimes form more than one bond, it's most common to find it with a single covalent bond in compounds like hydrogen iodide (HI) or iodine monochloride (ICl).