Question

An atom has 2 electrons in its M shell . What is its atomis number and its valency ?

Answer 1

Also Atomic number of atom = total number of electrons present in the atom. Therefore, atomic number of given element is equal to 12. And element having atomic number equal to 12 is Magnesium. (2 electrons in K shell, 8 electrons in L shell and 4 electrons in M shell).

Answer 2

both will be 2 atomic no. and its valency