Question

The nitride ion in lithium nitride is composed of:
A. 7 protons and 7 electrons
B. 10 protons and 7 electrons
C. 7 protons and 10 electrons
D. 10 protons and 10 electrons

Answer 1

Hint: Lithium nitride is a compound with chemical formula $L{i_3}N$. It is the only stable alkali metal nitride. It reacts with water to make lithium hydroxide and ammonia. Further, electrons are a type of subatomic particle with a negative charge and protons are a type of subatomic particle with a positive charge.

Complete step by step answer:
Lithium nitride is a solid which has a reddish-pink color and a high melting point. Its chemical formula is $L{i_3}N$. Its structure is as shown:

The nitride ion in this compound is ${N^{3 - }}$ which has a charge of – 3. Since, the atomic number of nitrogen is 7, so the number of protons is also 7 because the number of protons in the nucleus of the atom is equal to the atomic number (Z).
Now, the number of electrons will be 10 because the number of protons were 7 and further, 3 more electrons were added. (Because there is a charge of – 3 on the nitride ion).
So, there were 7+3=10 electrons.

Hence, option C is correct.

Note:
The nitrides of boron, vanadium, silicon, titanium and tantalum are very refractory, resistant to chemical attack, and hard and thus are useful as abrasives and in making crucibles. Lithium nitride is used to store hydrogen and is also used as a source of the nitride ion. Moreover, nitride compounds are also used as insulators