Group 15 includes nitrogen, phosphorus, arsenic, antimony, bismuth and moscovium. As we go down the group, there is a shift from non-metallic to metallic through metalloidic character. Nitrogen and phosphorus are non-metals, arsenic and antimony metalloids, bismuth and moscovium are typical metals. Molecular nitrogen comprises 78% by volume of the atmosphere. In the earth’s crust, it occurs as sodium nitrate, NaNO₃ (called Chile saltpetre) and potassium nitrate (Indian saltpetre). It is found in the form of proteins in plants and animals. Phosphorus occurs in minerals of the apatite family, Ca₉(PO₄)₆. CaX2 [X = F, Cl or OH] [e.g., fluorapatite Ca₉(PO₄)₆.CaF_2] which are the main components of phosphate rocks. Phosphorus is an essential constituent of animal and plant matter. It is present in bones as well as in living cells. Phosphoproteins are present in milk and eggs. Arsenic, antimony and bismuth are found mainly as sulphide minerals. Moscovium is a synthetic radioactive element. Its symbol is Mc, atomic number 115, atomic mass 289 and electronic configuration [Rn] 5f¹⁴6d¹⁰7s²7p³. Due to very short half life and availability in very little amount, its chemistry is yet to be established.

What is the maximum covalency of the nitrogen atom?

Four

The correct answer is option 4. Four.

The maximum covalency of the nitrogen atom is four.

Covalency refers to the number of covalent bonds an atom can form. For nitrogen, this can be understood by considering its electronic configuration and its ability to expand its valence shell:

Electronic Configuration:

Nitrogen has the electronic configuration 1s² 2s² 2p³.

In its ground state, nitrogen has five valence electrons (2s² 2p³).

Usual Covalency:

In most compounds, nitrogen forms three covalent bonds (e.g., \(NH_3\), where nitrogen forms three bonds with hydrogen). This is because three bonds plus one lone pair completes its octet.

Expanded Covalency:

However, nitrogen can also form four covalent bonds in certain compounds by using its lone pair for bonding. A classic example is the ammonium ion \((NH_4^+)\), where nitrogen forms four bonds with hydrogen.

Details of Maximum Covalency:

When nitrogen forms four covalent bonds, it effectively utilizes all its valence electrons for bonding, including the lone pair. This situation doesn't exceed the octet rule because the nitrogen atom still accommodates only eight electrons in its valence shell (four pairs of bonding electrons).

Ammonium ion \((NH_4^+)\): In this ion, nitrogen forms four single bonds with four hydrogen atoms.

\( NH_3 + \text{H}^+ \rightarrow NH_4^+ \)

Therefore, while nitrogen typically shows a covalency of three in most of its compounds, it can achieve a maximum covalency of four, particularly when it forms an additional bond using its lone pair. So, the correct answer is: 4. Four