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Question: Answered & Verified by Expert
The ionisation energy of an electron in the ground state of helium atom is $24.6 \mathrm{eV}$. The energy required to remove both the electron is
PhysicsNuclear PhysicsKCETKCET 2013
Options:
  • A $51.8 \mathrm{eV}$
  • B $79 \mathrm{eV}$
  • C $38.2 \mathrm{eV}$
  • D $49.2 \mathrm{eV}$
Solution:
2768 Upvotes Verified Answer
The correct answer is: $79 \mathrm{eV}$
Ionisation energy in ground state $=24.6 \mathrm{eV}$
Energy required to remove $2^{n}$ electron from $\mathrm{He}^{2+}$
Ionisation energy in ground state $=24.6 \mathrm{eV}$
Energy required to remove $2^{n}$ electron from $\mathrm{He}^{2+}$
$=Z^{2}(13.6) \mathrm{eV}=(2)^{2}(13.6)=54.4 \mathrm{eV}$
$=Z^{2}(13.6) \mathrm{eV}=(2)^{2}(13.6)=54.4 \mathrm{eV}$
So, total energy required $=24.6+54.4=79 \mathrm{eV}$

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