Some atoms are exceptions to the octet rule by having an expanded octet. which characteristic is needed for an atom to have an expanded octet?
a. the atom has empty d-orbitals.
b. the atom has more than eight valence electrons before bonding.
c. the atom has empty p-orbitals.
d. the atom has fewer than eight valence electrons after bonding.

B. The atom has more than eight valence electrons before bonding.

Explanation:

Expansion of the octet rule occurs only with atoms of non-metallic elements from the third period onwards, ie having three or more electronic layers. This is because these atoms have empty orbitals that can accommodate 10, 12 or more electrons. These atoms have more than eight valence electrons before bonding.

An example of a chemical element whose atoms may contract is phosphorus (P), which belongs to family 15 or VA of the periodic table. This means that it has five electrons in the valence shell and, according to the octet theory, should receive three more electrons to be stable with eight electrons.  However, the phosphorus is the element can be the central element of a compound and for this reason it makes five covalent bonds with four carbon atoms. Since the phosphorus atom shares five pairs of electrons, it has a total of ten electrons in the valence shell, meaning it did not follow the octet rule, but there was an expansion of its octet.

it takes on an electronical energy