The longest wavelength that the singly ionized helium atom in its ground state will obsorb is

Options

A. `912 Å`
B. `304 Å`
C. `606 Å`
D. `1216 Å`

Answer

B

Explanation

`lambda = (912 Å)/(Z^(2) [(1)/(n_(1)^(2)) - (1)/(n_(2)^(2))]`
for singly ionized helium atom `Z = 2`
for the wavelength to be longest, `n_(1) = 1, n_(2) = 2`
`:. lambda = (912 Å)/((2^(2))[1 - (1)/(4)]) = (912)/(3) = 304 Å`