Solution:

Energy of electron in Bohr orbit is given by:

E_n = -13.6 / n² eV

For first orbit (n = 1):

E₁ = -13.6 eV

For second orbit (n = 2):

E₂ = -13.6 / 4 = -3.4 eV

Required excitation energy:

ΔE = E₂ - E₁

ΔE = (-3.4) - (-13.6)

ΔE = 10.2 eV

Answer: 10.2 eV