Final answer:
In molecules with identical atoms, such as Cl2, a pure covalent bond is formed, with electrons being shared equally. This results in a nonpolar molecule. Each chlorine atom in Cl2 has eight valence electrons: six nonbonding and two bonding.
Step-by-step explanation:
When atoms within a molecule are identical, as with diatomic elements like chlorine (Cl2), the electrons that form the bond between these atoms are shared equally. This equal sharing is characteristic of a pure covalent bond. The equal probability of electron distribution near each nucleus implies that there is no net dipole moment, and each chlorine atom ends up with six nonbonding electrons and two electrons in the single covalent bond, matching the valence electron count of the noble gas argon.
In a pure covalent bond, such as the bond in Cl2, the electron pairs are shared equally, leading to a nonpolar molecule. This is in contrast to polar covalent bonds or ionic bonds, where the electron pairs are shared unequally, or one atom donates an electron to another, respectively. An example of a molecule that lies between pure covalent and ionic bonding is NaCl, where the electron from Na is transferred to Cl, creating Na+ and Cl− ions.
The shared electrons in Cl2 form what is known as a single bond, with each chlorine atom interacting with eight valence electrons: the six in the lone pairs and the two in the single bond.