Question

if an atom has atomic mass 4 Nd 2 protons in its nucleus,how many neutrons does it have??

Answer 1

Number of protons = 2Atomic Mass = 4But Atomic mass = protons + neutrons
So, we get number of neutrons = 4 - 2 = 2

Answer 2

☆$\red {HELLO\:DEAR}$☆

Helium atom has two neutrons.

The mass of an atom is the sum of the masses of protons and neutrons present in its nucleus.

Since helium atom has two protons, mass contributed by the two protons is (2 × 1) u = 2 u.

Then, the remaining mass (4 − 2) u = 2 u is contributed by 2u/1u = 2 neutrons.

☆$\green {VISHU\:PANDAT}$☆

☆$\blue {FOLLOW\:ME}$☆