Why are \(d\) orbitals sometimes used to form hybrid orbitals? Which period of elements does not use \(d\) orbitals for hybridization? If necessary, which \(d\) orbitals \((3 d, 4 d, 5 d, \text { or } 6 d)\) would sulfur use to form hybrid orbitals requiring \(d\) atomic orbitals? Answer the same question for arsenic and for iodine.

d orbitals can be involved in the formation of hybrid orbitals to accommodate more electrons in bonding and thus result in molecules with expanded octets. When elements from the third period and below form hybrid orbitals, they can use their d orbitals, which have the same energy level as their s and p orbitals, to create hybrid orbitals with more than 4 electron pairs (up to 6 electron pairs in some cases). This can allow for more bonding with other atoms and stabilize the molecule.

Elements in the second period do not use d orbitals in hybridization. This is because the elements in the second period have only s and p orbitals available for hybridization, as the 2d orbitals do not exist. The first available d orbitals are 3d orbitals, which can be used by elements in the third period and higher.

Sulfur is in the 3rd period and the 16th group of the periodic table. If necessary, sulfur will use 3d orbitals to form hybrid orbitals. Arsenic is in the 4th period and the 15th group of the periodic table. If necessary, arsenic will use 4d orbitals to form hybrid orbitals. Iodine is in the 5th period and the 17th group of the periodic table. If necessary, iodine will use 5d orbitals to form hybrid orbitals. In summary, d orbitals are used in hybrid orbitals for elements of the third period and below, allowing the formation of expanded octets. The second period of elements does not use d orbitals for hybridization as they only have s and p orbitals. Sulfur, arsenic, and iodine would use the d orbitals of their respective energy levels (3d, 4d, and 5d) for forming hybrid orbitals if necessary.