Question

An iron m2 contains 10 electrons and 12 neutrons. What is the atomic number and mass number of the elements

Answer 1

If M2 has 10 electrons it means the neutral atom M has 12 electrons.

That's because it loses 2 electrons to form an ion with charge positive 2

 A neutral atom with 12 electrons must have12 protons

∴ Mass number of M = 12+12 = 24 (Sum no. of Neutrons and protons)

   Atomic number of M = 12 (No. of protons)