$(i)$ Atomic number: The atomic number of an element is the total number of protons present in the atom of that element. For example, nitrogen has $7$ protons in its atom. Thus, the atomic number of nitrogen is $7$.

$(ii)$ Mass number: The mass number of an element is the sum of the number of protons and neutrons present in the atom of that element. For example, the atom of boron has $5$ protons and $6$ neutrons. So, the mass number of boron is $5+6=11$.