An element has $13$ electrons in the $M$ shell in its ground state. Which element could it be?

The Aufbau principle is obeyed in which of the following electronic configurations?

Which of the following statements is not correct?

If an electron has a spin quantum number of $+ \frac{1}{2}$ and a magnetic quantum number of $- 1$,it cannot be present in an

An electron has a magnetic quantum number of $-3$. Its principal quantum number can be

If the nitrogen atom had electronic configuration $1s^7$,it would have energy lower than that of the normal ground state configuration $1s^2, 2s^2, 2p^3$ because the electrons would be closer to the nucleus. Yet,$1s^7$ is not observed because it violates: