Electron Valence

Its value is the number of electrons in an incomplete outermost shell.

A completed outer shell contains a valence of zero. Copper for example, contain a Valence of 1 because there is one electron in the outermost shell of the copper Atom.

Sub-shells

Though not indicated in the illustrations, all of the shells except K shell are divided into sub-shells. This sub-division accounts for the different kinds of the orbits in the similar shell. For example, electrons in the one sub-shell will contain circular orbits whenever other electrons of the similar shell will contain elliptical orbit. This particular sub-division accounts for the magnetic properties of the atom.