An electron revolving in a stationary orbit of an atom absorbs some energy and the electron may jump over to an orbit of higher energy. This process is called excitation and the atom is said to be in the excited state. The energy, thus absorbed to movefrom one orbit to other is called excitation potential. Energy of electron in ground state of hydrogen atom, E1=−13.6eV[∵En=‌
−13.6
n2
eV] ∴ Energy of electron in first excited state of hydrogen atom, E2=‌
−13.6
22
=−3.4eV Hence, the excitation potential of hydrogen atom in first excited state, E‌‌=E2−E1 ‌‌=−3.4−(−13.6)=10.2eV