Question

What is the covalency of phosphorus atom in ground state?
A. 3
B. 4
C. 5
D. 1

Answer 1

Hint: Phosphorus is an element that belongs to the nitrogen family having atomic number 15. It has 5 electrons in its outermost orbital $(3{s^2} - 3{p^3})$ thereby it can form either 3 or 5 covalent bonds. It can show a maximum covalency equal to its group number-10 for p block elements.

Complete step-by-step answer:
When an element shares its electrons with other atoms of the same or different elements to complete its octet and to acquire stable electronic configuration, it is called its covalency.
We can find out the maximum covalency of elements by calculating the number of orbitals in the outermost shell. We can also do this by calculating the number of electrons present in the outermost shell. For s block elements it is atomic group number but for p block elements it is group number-10.
Phosphorus belongs to group 15 that is the nitrogen family of p block. Electronic configuration of phosphorus is \[1{s^2}2{s^2}2{p^6}3{s^2}3{p^3}\].
Its maximum covalency will be 15-10, that is 5. But in ground state, it can only lose three electrons of 3p orbitals as the two electrons of 3s are intact due to high nuclear charge. So, we can say that the covalency of phosphorus atoms in ground state is 3.

Hence, the correct option is (A).

Note: There is a difference between valency and covalency such that valency is the number of electrons that an atom either loses or gains in order to stabilise itself whereas covalency is the maximum number of covalent bonds an atom forms using its empty orbitals.