In $H$ atom,an orbit has a diameter of about $16.92 \ \mathring{A}$. What is the maximum number of electrons that can be accommodated in this orbit?

Which of the following graphs is correct for the kinetic energy $(K.E.)$ of an electron in the $n^{th}$ orbit of a hydrogen-like atom?

Identify the correct statements from the following:
$A$. Heisenberg uncertainty principle is applicable to electrons.
$B$. The size of $2p_x$ orbital is less than the size of $3p_x$ orbital.
$C$. The energy of $2s$ orbital of $H$ atom is equal to the energy of $2s$ orbital of $Li$.
$D$. The electronic configuration of $Cr$ is $[Ar]3d^5 4s^1$.

When the excited electron of a $H$ atom from $n=5$ drops to the ground state,the maximum number of emission lines observed are $.......$

Which of the following statements is $CORRECT$ :
$(I)$ Where orbitals are available in degenerate sets,maximum spin multiplicity is observed.
$(II)$ Where two electrons occupy the same shell,they may have same spins.
$(III)$ All noble gases do not have the same valence shell electronic configuration.

Match the items in Column-$A$ with the items in Column-$B$.

Column-$A$	Column-$B$
$(1)$ Dalton	$(A)$ Photoelectric effect
$(2)$ Maxwell	$(B)$ Wave theory
$(3)$ Huygens	$(C)$ Atomic theory
	$(D)$ Electromagnetic radiation