Thus, the electrons farthest from the nucleus are more easily freed from their orbits than electrons in the inner orbits. Orbital Shells To have a balanced or stable atom, the number of electrons must equal the number of protons in the nucleus. The more electrons an atom has, the more orbits or shells it contains. For instance, hydrogen has only one electron orbiting in one shell, while plutonium has 94 electrons orbiting in seven shells. Not all of the electrons in an atom can fit into one shell, so additional shells must exist to accommodate them.
Heavier atoms have even more shells up to seven.
Note that these numbers are only capacities. A given shell can contain fewer electrons than its capacity. For instance, silver has only 18 electrons in its fourth shell, which has a capacity of 32. Next month s installment will cover the valence shell and electron energy level. All rights reserved.