n=1 means ground state n=2 means 1st excited state n=3 means 2‌nd ‌ excited state Remember: n‌th ‌ excited state means n=n+1 We know energy of an atom is given by Energy (E)=−13.6×‌
Z2
n2
=−13.6×‌
1
9
[∵Z= atomic number =1 for hydrogen atom ] =−1.51‌eV