ΔE = 2.18 × 10⁻²¹ kJ
Using Bohr Energy Equation,
ΔE = - R (1/nₐ² - 1/nₓ²)
Where;
R = Rydberg's constant = 2.18 × 10⁻¹⁸ J
nₐ = Infinity = ∞ (electron removed from H atom)
nₓ = 1 (Ground state of H atom)
Putting Values in equation 1,
ΔE = - 2.18 × 10⁻¹⁸ J × ( 1/∞² - 1/1²)
ΔE = - 2.18 × 10⁻¹⁸ J × ( 0 - 1)
ΔE = - 2.18 × 10⁻¹⁸ J × (-1)
ΔE = 2.18 × 10⁻¹⁸ J
ΔE = 2.18 × 10⁻²¹ kJ