Question

Why does the energy of an electron will increase when the number of shells increases.

Answer 1

The binding energies of the electrons go down as the shell number increases. When a place on an internal energy shell is made available, an electron situated on a higher shell fills the gap by jumping to fill the place left over, increasing the strength of its bond to the nucleus.

Step-by-step explanation:

Answer 2

The farther away valence electrons are from the nucleus, the more reactive the element will be. So more shells cause a greater distance from the nucleus, making the atom more reactive.