The wave function $\left(\Psi \right)$ of $2 \mathrm{s}$ is given by

${\Psi }_{2\mathrm{s}}=\frac{1}{2\sqrt{2\pi }}{\left(\frac{1}{{\mathrm{a}}_0}\right)}^{1/2}\left(2-\frac{\mathrm{r}}{{\mathrm{a}}_0}\right){\mathrm{e}}^{-\mathrm{r}/2{\mathrm{a}}_0}$

At $\mathrm{r}={\mathrm{r}}_0$, radial node is formed. Thus, ${\mathrm{r}}_0$ in terms of ${\mathrm{a}}_0$

Arrange the following orbitals in decreasing order of energy.

A. $\mathrm{n}=3, \mathrm{l}=0, \mathrm{m}=0$
B. $\mathrm{n}=4, \mathrm{l}=0, \mathrm{m}=0$
C. $\mathrm{n}=3, \mathrm{l}=1, \mathrm{m}=0$
D. $\mathrm{n}=3, \mathrm{l}=2, \mathrm{m}=1$

The correct option for the order is:

Electrons in a cathode ray tube have been emitted with a velocity of $1000 {\mathrm{ms}}^{-1}$. The number of following statements which is/are true about the emitted radiation is

Given : $\mathrm{h}=6\times {10}^{-34}\mathrm{Js},{\mathrm{m}}_{\mathrm{e}}=9\times {10}^{-31} \mathrm{kg}$

(A ) The deBroglie wavelength of the electron emitted is $666.67 \mathrm{nm}$

(B ) The characteristic of electrons emitted depend upon the material of the electrodes of the cathode ray tube.

(C) The cathode rays start from cathode and move towards anode.

(D ) The nature of the emitted electrons depends on the nature of the gas present in cathode ray tube..

Which one of the following sets of ions represents a collection of isoelectronic species?

(Given : Atomic Number $: \mathrm{F}:9,\mathrm{Cl}:17,\mathrm{Na}=11$

$\mathrm{Mg}=12,\mathrm{Al}=13, \mathrm{K}=19,\mathrm{Ca}=20,\mathrm{Sc}=21)$