In an atom, total number of electrons having quantum numbers $$\mathrm{n}=4,\left|\mathrm{~m}_l\right|=1$$ and $$\mathrm{m}_{\mathrm{s}}=-\frac{1}{2}$$ is _________.

The value of Rydberg constant $$(R_H)$$ is $$2.18 \times 10^{-18} \mathrm{~J}$$. The velocity of electron having mass $$9.1 \times 10^{-31} \mathrm{~kg}$$ in Bohr's first orbit of hydrogen atom = ________ $$\times 10^5 \mathrm{~ms}^{-1}$$ (nearest integer).

The maximum number of orbitals which can be identified with $$\mathrm{n}=4$$ and $$m_l=0$$ is _________.

The de-Broglie's wavelength of an electron in the $$4^{\text {th }}$$ orbit is ________ $$\pi \mathrm{a}_0$$. ($$\mathrm{a}_0=$$ Bohr's radius)