Question

helium atom has a atomic mass 40 and two protoans in its nucleus.How many neutron does it have?

Answer 1

Protons + neutrons= atomic mass
so helium atom has 40-2=38 neutrons ..
Hope it helps you!!

Answer 2

Well ,This is a hypothetical question .Generally Atomic mass of Helium is 4 amu.

I hope this question was Based on The Formula ,Atomic mass=Number of neutrons+Number of protons.

Given ,Atomic mass of Helium =40

Number of protons=2

Hence ,Number of neutrons=40-2=38

Number of Neutrons in the helium atom of mass 40 possessing 2 protons is 38 neutrons .