When a chlorine atom comes into contact with another atom, they form a covalent bond. This type of bond occurs when two or more atoms share their outermost electrons, creating a strong bond between the atoms involved. In the case of chlorine, it has seven electrons in its outermost shell, and it needs one more electron to complete its octet. When chlorine comes in contact with another atom that has an extra electron, the chlorine atom will take the extra electron and form a covalent bond with it. This bond is formed by the covalent sharing of electrons between the two atoms, creating a stable molecule or compound.