Question

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

Answer 1

Given,

element- helium ,

mass number =4,

protons = 2

to find out neutrons,

here,

helium's atomic number is 2

mass number - atomic number

4-2=2

hence,

there are 2 neutrons.

Answer 2

Explanation:

The mass of an atom is given by the sum of the masses of protons and neutrons present in the nucleus. Since helium atom has a atomic mass of 4 u and it has two protons. Two protons contribute 2 u to atomic mass. Hence, it must contain 2 neutrons.