The magnetic quantum number for an electron when the value of principal quantum number is $2$ can have ............ values.

Which of the following electronic configurations is more stable?

When the $3d$ orbital is complete,the next electron will enter the

How many unpaired electrons are present in the $Ni^{2+}$ cation (atomic number $= 28$)?

In a multi-electron atom,which of the following orbitals have the same energy in the absence of magnetic and electric fields? $(a) n = 1, l = 0, m = 0, (b) n = 3, l = 0, m = 0, (c) n = 2, l = 1, m = 1, (d) n = 3, l = 2, m = 1, (e) n = 3, l = 2, m = 0$

Which of the following species must have the maximum number of electrons in the $d_{xy}$ orbital?