Question

Covalency of nitrogen in ammonium ion is:
A) 2
B) 3
C) 4
D) 5

Answer 1

Hint: The answer to the question here includes the concept of inorganic chemistry which gives definition of covalency as the number of covalent bonds formed by the central atom in a molecule.

Complete step by step answer:
- Covalency of a bond is defined as the total number of covalent bonds formed by the central atom with the other atom.
- Covalent bonds are those bonds which share the electron pairs between the atoms and are called bonding pairs of electrons.
- Nitrogen on the other hand has a total five electrons in its outermost shell and thus it can accept three electrons to fulfil the octet structure and thus its valance is three with a lone pair of electrons present on it.
- In the case of ammonium ion with molecular formula $N{{H}_{4}}^{+}$ there are three covalent bonds where three hydrogen atoms are bound covalently to the central nitrogen atom to fill the octet structure. But the fourth hydrogen atom is coordinately bound to nitrogen atom.
Therefore, the fourth bond in ammonium ion is a coordinate covalent bond and this is also a maximum covalency of nitrogen.
Thus, according to the definition of covalency the total number of covalency in ammonium ion is four.
So, the correct answer is “Option C”.

Note: Be concentrated about the fact that coordinate bond can also be formed as coordinate covalent bond only if there are lone pairs of electrons present on an atom to donate its electrons and do not confuse that it does not come under covalent bond count.