Question

(a) atom is considered electrically neutral. Explain.(b) state the valency of helium.(c) if an atom has atomic mass 4 and 2 protons in its nucleus. How many neutrons does it have?

Answer 1

(a) atoms are electrically neutral becoz number of electrons = number of protons.e.g amount of negative charge equals amount of positive charge .

(b) configuration of He = 1s²
helium is inert gas , this is complete subshell by only 2 electrons ,
valancy of helium = 0

(c ) atomic mass = no of protons + no of neutrons
4 = 2 + no of neutrons

no of neutrons = 2