Answer:
-20.2 * 10^-18 J
Step-by-step explanation:
From;
E = hc/λ
h= planks constant = 6.6 * 10^-34 Js
c= speed of light = 3 * 10^8 ms-1
λ = wavelength = 10.8 * 10^-9 m
Substituting values;
E = 6.6 * 10^-34 * 3 * 10^8/ 10.8 * 10^-9
ΔE = -1.8 * 10^-17 J
But for ground state E1=−13.6eV or -2.176 * 10^-18 J
From;
ΔE = E4 - E1
E4 = ΔE + E1
E4 = (-1.8 * 10^-17) + (-2. 176* 10^-18)
E4 = -20.2 * 10^-18 J