Question

If the energy of a hydrogen atom in nth orbit is $E_{n}$, then energy in the nth orbit of a singley ionized helium atom will be.

• A. $4E_{n}$
• B. $E_{n}/4$
• C. $2E_{n}$
• D. $E_{n}/2$

Answer 1

Answer: (A)

$4E_{n}$

Answer 2

$E_{n} \propto Z^{2}$ ⇒ $\frac{(E_{n})_{He}}{(E_{n})_{H}} = \frac{Z_{He}^{2}}{Z_{H}^{2}} = 4$ ⇒ $(E_{n})_{He} = 4 \times (E_{n})_{H}$