. The covalency of central atom is maximum in
Covalency refers to the tendency of an element to share its electrons with other atoms of the same or different elements to acquire a stable electronic configuration.
Since there is sharing of electrons, there is no ion formation.
Covalency is, thus, also defined as the measure of the number of bonds that are formed by the central atom of a covalent compound.
Thus, to find which of the given molecules has maximum covalency, we must look at the number of bonds formed by their respective central atoms.
Since, the central atom C is attached to 4 bonds in total (1 with H and 3 with N), its covalency = 4
Ammonium cation is formed by the protonation of ammonia base. Since, the central atom N is attached to 4 bonds in total, each with H, its covalency = 4.
Phosphorus pentachloride has P as the central atom. Since
Water molecule is formed by the combination of a divalent oxygen atom and two hydrogen atoms.
There are a total of two covalent bonds that connect the O atom to the H atoms. Hence, the covalency = 2.
Thus, the covalency of central atom is maximum in Phosphorus pentachloride.
Hence, the correct option is C: PC15.