Which shell has less energy for electrons?

The first inner shell, often referred to as the K shell, is closest to the nucleus of the atom. This proximity to the nucleus results in a stronger electrostatic attraction between the positively charged protons in the nucleus and the negatively charged electrons. Because of this stronger attraction, electrons in the first inner shell have lower potential energy compared to those in outer shells.

In general, the energy of electrons increases as you move to shells that are further away from the nucleus. Outer shells, such as the second or third inner shell, typically house electrons with higher potential energy due to the reduced attraction they experience from the nucleus. As such, electrons in these outer regions can be more easily lost and are associated with higher energy levels.

Therefore, the first inner shell is indeed the shell with the least energy for electrons, making it the correct choice.