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12. atoms — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics12. atoms1 Mark
MCQ
The energy required to remove the electron from a singly ionized Helium atom is $2.2\, times$ the energy required to remove an electron from Helium atom . The total energy required to ionize the Helium atom completely is......$eV$
  • A
    $20$
  • ✓
    $79$
  • C
    $109$
  • D
    $34$
✓

Answer

Correct option: B.
$79$
b
Energy required to remove e - from singly

ionized helium atom ${ = \frac{{(13.6){Z^2}}}{{{1^2}}} = 54.4\,{\text{eV}}}$

$(\because Z=2)$

Energy required to remove $e^-$ from helium atom $=x\,eV$

According to question, $54.4 \mathrm{eV}=2.2 \mathrm{x} \Rightarrow \mathrm{x}$

$=24.73 \mathrm{eV}$

Therefore, energy required to ionize helium atom $=(54.4+24.73)eV$ $=79.12 \mathrm{eV}$

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