Question

atomic no of aluminium is 13 and mass no is 27. calculate no of electron, proton & neutrons in its atom?

Answer 1

no. of protons = atomic no. of the given element = 13
no. of electrons = atomic no. of the given element = 13
(since 13 electrons are needed to balance 13 protons)
no. of neutrons = atomic mass no. - no. of protons = 27 - 13 = 14
(aluminium's atomic mass is 27,This is total of total no. of particles in an atom's nucleus, so an 'average' atom of Al contains 27 particles in its nucleus. We know that 13 of those particles are protons. The rest must be neutrons. So, an atom of mercury contains 27 - 13 = 14 neutrons)

Answer 2

No of protons and neutron =13and no of electron=27-13=14