In chemistry and atomic physics, an electron shell may be thought of as an orbit that electrons follow around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" (also called the "K shell"), followed by the "2 … See more

Each shell is composed of one or more subshells, which are themselves composed of atomic orbitals. For example, the first (K) shell has … See more

Although it is sometimes stated that all the electrons in a shell have the same energy, this is an approximation. However, the electrons in one subshell do have exactly the same level of energy, with later subshells having more energy per electron than earlier ones. … See more

• Periodic table (electron configurations)
• Electron counting
• 18-electron rule
• Core charge See more

In 1913, Niels Bohr proposed a model of the atom, giving the arrangement of electrons in their sequential orbits. At that time, Bohr allowed the capacity of the inner orbit of the … See more

Each subshell is constrained to hold 4ℓ + 2 electrons at most, namely:
• Each s subshell holds at most 2 electrons See more

The list below gives the elements arranged by increasing atomic number and shows the number of electrons per shell. At a glance, the subsets of the list show obvious patterns. In particular, every set of five elements ( electric blue) before each See more