Atoms - Result Question 33
35. The energy of hydrogen atom in nth orbit is $E_n$, then the energy in nth orbit of single ionised helium atom will be
[2001]
(a) $4 E_n$
(b) $E_n / 4$
(c) $2 E_n$
(d) $E_n / 2$
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Answer:
Correct Answer: 35. (a)
Solution:
- (a) We have $E_n=\frac{-2 \pi^{2} m K^{2} Z^{2} e^{4}}{n^{2} h^{2}}$. For helium $Z=2$. Hence requisite answer is $4 E_n$
The energy required to ionise an atom is called ionisation energy. It is energy required to make the electron Jump from the present orbit to the infinite orbit.
$ \begin{aligned} & E _{\text{ionisation }}=E _{\infty}-E_n=0-(-13.6 \frac{Z^{2}}{n^{2}}) \\ & =+\frac{13.6 z^{2} eV}{n^{2}} \end{aligned} $
