What is the orbital angular momentum of an electron in a $2s$-orbital?

Which of the following sets of species has the $3^{rd}$ principal energy level $(n=3)$ completely filled?

An orbital with one angular node shows three maxima in its radial probability distribution curve, the orbital is

Using $s, p, d, f$ notations,describe the orbital with the following quantum numbers:
$(a) n=2, l=1$
$(b) n=4, l=0$
$(c) n=5, l=3$
$(d) n=3, l=2$

The electronic configurations of four elements are given in brackets: $L\,(1s^2, 2s^2 2p^1)$; $M\,(1s^2, 2s^2 2p^5)$; $Q\,(1s^2, 2s^2 2p^6, 3s^1)$; $R\,(1s^2, 2s^2 2p^2)$. Which element would most readily form a diatomic molecule?

The electron configuration of $Fe^{3+}$ is (atomic number of $Fe = 26$)