The mass number of fe2+ is 56. how many neutrons are there in a single fe2+ atom?

the number of neutrons present in a single   atom is 30

Explanation: Given atom is  which is basically ion of iron from which two electrons have been removed .

Thus Atomic number of , Z = 26

Mass number of  , M=56

Now we know that the mass number of the atom (M) is equal to the sum of the number of protons(P) and neutrons(N) in the nucleus ,i.e., M=P+N ----(A)

Also the number of protons in the nucleus of the atom is equal to the atomic number (Z).

Therefore number of protons , P=Z= 26    

Using equation (A) we get

56=26+ N

=>N=30

Thus the number of neutrons present in a single   atom is 30

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