The correct order of ionic radii of $Ce, La, Pm$ and $Yb$ in $+3$ oxidation state is

In organic reactions,sodium in liquid ammonia is used as

The function $f(x) = \log(1 + x) - \frac{2x}{2 + x}$ is increasing on

Which of the following is the most stable ecosystem?

Two spheres $A$ and $B$ are kept very near to each other. $A$ is negatively charged and $B$ is earthed. The true statements are:
$(A)$ Charge on $B$ is zero
$(B)$ Potential at $B$ is zero
$(C)$ Charge is uniformly distributed on $A$
$(D)$ Charge is non-uniformly distributed on $A$

In a hydrogen-like atom,an electron makes a transition from an energy level with quantum number $n$ to another with quantum number $(n - 1)$. If $n >> 1$,the frequency of the emitted radiation is proportional to: