MCQ
Potential energy of electron present in $He^+$ is
- A$\frac{{{e^2}}}{{2\pi { \in _0}r}}$
- B$\frac{{3{e^2}}}{{4\pi { \in _0}r}}$
- ✓$\frac{{ - {e^2}}}{{2\pi { \in _0}r}}$
- D$\frac{{ - {e^2}}}{{4\pi { \in _0}{r^2}}}$
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(Atomic numbers $Ce =58, Gd =64$ and $Eu =63 .)$
$(a)$ $\left( NH _{4}\right)_{2}\left[ Ce \left( NO _{3}\right)_{6}\right]$
$(b)$ $Gd \left( NO _{3}\right)_{3}$ and
$(c)$ $Eu \left( NO _{3}\right)_{3}$
Answer is :