What term is used to label the energy levels of electrons?

Answer : The term used to label the energy levels of electrons is, Principle Quantum Numbers (n).

Explanation :

There are 4 quantum number.

Principle Quantum Numbers : It describes the size of the orbital or energy levels of electrons. It is represented by n. n = 1,2,3,4....

Azimuthal Quantum Number : It describes the shape of the orbital. It is represented as 'l'. The value of l ranges from 0 to (n-1). For l = 0,1,2,3... the orbitals are s, p, d, f...

Magnetic Quantum Number : It describes the orientation of the orbitals. It is represented as . The value of this quantum number ranges from . When l = 2, the value of

Spin Quantum number : It describes the direction of electron spin. This is represented as . The value of this is for upward spin and for downward spin.

Hence, the term used to label the energy levels of electrons is, Principle Quantum Numbers (n).