Final answer:
The halogens all have valence electrons in p orbitals, but these electrons are not in the same energy level due to each element's increasing principal quantum number. Halogens form diatomic molecules, with each atom sharing an unpaired electron to complete their valence electron octet, resulting in a stable covalent bond.
Step-by-step explanation:
The halogens, which include elements such as fluorine, chlorine, bromine, and iodine, all have seven valence electrons in their outer shell. Their general electron configuration is ns²np⁵, meaning that in each case, there is a pair of electrons in an s orbital and five electrons in p orbitals. The electrons occupy different energy levels as we move down the group, this is because each successive element in the halogen group has an additional electron shell. For instance, the valence electrons of fluorine exist in the 2p orbital, while chlorine has valence electrons in the 3p orbitals, bromine in the 4p, and iodine in the 5p orbitals. Therefore, while the valence electrons of all halogens are in p orbitals, they are not in the same energy level due to the increasing principal quantum number (n).
All halogens form diatomic molecules, such as F₂, Cl₂, Br₂, and I₂, by sharing their unpaired electron to achieve a stable electronic structure. For example, in fluorine (F₂), each atom shares its unpaired electron located in the 2p orbital, resulting in a single covalent bond between them. This principle of sharing electrons to achieve a full outer shell is underscored by the valence bond theory, which provides insights into the types of orbital overlaps that occur during bond formation. These overlaps result in the formation of stable molecules, with the valence shell of each atom in the diatomic molecule achieving a complete octet, indicative of the most stable electron arrangement.