Which of the following gases does not have an octet or eight electrons in the outer shell?

What is the difference between $2p_x, 2p_y,$ and $2p_z$ orbitals?

The minimum number of quantum numbers required to specify an orbital in an atom is

Which one of the following sets of quantum numbers represents an impossible arrangement?

In a multi-electron atom,which of the following orbitals described by the three quantum numbers will have the same energy in the absence of magnetic and electric fields?
$1. n = 1, l = 0, m = 0$
$2. n = 2, l = 0, m = 0$
$3. n = 2, l = 1, m = 1$
$4. n = 3, l = 2, m = 0$
$5. n = 3, l = 2, m = 0$

For both $2p$ and $3s$ orbitals,the value of $(n + l)$ is equal to $3$. Which of these has lower energy and why?