Question

The nitrogen atom has an atomic number $7$ and oxygen has an atomic number $8$. Calculate the total number of electrons in nitrate ions.
A) $8$
B) $16$
C) $32$
D) $24$

Answer 1

Hint: The number of electrons is always equal to the atomic number of that element. The nitrate ion has one nitrogen atom and three oxygen atoms and one can guess the structure of nitrate ion. To get the desired answer one can do the sum of all the number of electrons present in the structure.

Complete step by step answer:
1) First of all let's know about the structure of nitrate ion and analyze it stepwise, the molecular formula of nitrate ion is $N{O_3}^ - $ where one nitrogen atom and three oxygen atoms are present.
2) The nitrate ion is an anionic form of ion which means it is a negatively charged species and has an extra electron as its charge.
3) The number of electrons present in an atom is always equal to the atomic number or number of protons present in that element. While calculating the total number of electrons in nitrate ion one must remember that with the sum of the number of electrons the anionic electrons are also taken into count.
4) so, the total number of electrons in the nitrate ion $N{O_3}^ - = 1 \times 7 + 3 \times 8 + 1 = 32$

So, the correct answer is Option C.

Note:
The nitrate ion is an anionic form ion. While calculating the total number of electrons in nitrate ion one must remember that with the sum of the number of electrons the anionic electrons are also taken into count. But in case the cation is present then one electron is subtracted as cation is formed due to deficiency of electron.