Question

Nitrogen atom has atomic mass of 14 u and has 7 protons in its nucleus. How many neutrons does it have?​

Answer 1

Answer- The above question is from the chapter 'Structure of Atom'.

Let's know about atomic number and mass number first.

Atomic Number- The atomic number of an element is the number of protons present in the nucleus of that element.

Atomic number is represented by Z.

It is also called Proton Number.

For an atom of an element, number of protons = number of electrons = Atomic Number

But the above relation is not true for ions of elements.

For example:

Let's take an element Sodium.

Number of protons = 11

Number of electrons = 11

∴ Atomic number (Z) = 11

Mass Number- The mass number is the number of nucleons i.e. protons and neutrons present in the nucleus of the element.

It is denoted by A.

It is also called Atomic Mass.

For an atom of an element, atomic mass = mass of protons + mass of neutrons

It is true for ions.

For example:

Let's take an element Fluorine.

Number of protons = 9

Number of neutrons = 10

∴ Mass Number (A) = 19

Given question: Nitrogen atom has atomic mass of 14 u and has 7 protons in its nucleus. How many neutrons does it have?​

Answer: Number of protons = 7

⇒ Atomic Number (Z) = 7

Atomic mass = 14 u

Number of protons + Number of neutrons = Atomic Mass

7 + Number of neutrons = 14

Number of neutrons = 14 - 7

Number of neutrons = 7

∴ Number of neutrons in Nitrogen atom = 7