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CBSE Class 9 Science Question 27 of 34

Structure of the Atom — Question 2

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Question

Question 2

Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?

Answer

Given,

Atomic mass of helium atom = 4u,

2 protons in helium nucleus

We know,

Atomic mass = number of protons + number of neutrons

4 = 2 + number of neutrons

So, number of neutrons = 4 – 2 = 2

Hence, Helium has 2 neutrons.