What is the maximum number of electrons that can occupy the first shell of an atom ?

What is the maximum number of electrons in the M-Shell ?

The number of maximum electrons in N shell is

What is the mass number of an element, the atom of which contains two protons, two neutrons and two electrons?

Atomic mass of an element is equal to the sum of number of

If an atom X has 10 electrons and its mass number is 22, calculate number of protons for X