Familiarity with the periodic table is central to the understanding to the arrangement of electrons within atoms.
For any element, the
valence (outermost)
electrons are involved in
bonding, the
remaining electrons being known as
core electrons.The number of valence electrons and the type of orbitals occupied by core and valence electrons can be correlated with the position of the element in the periodic table.
- The number of valence electrons equals the last digit of the Group Number.
- All electrons on an atom occupy orbitals which are grouped in subshells. The number of groups in blocks of the periodic table (two at the left side, ten in the middle and six at the right) reflect the maximum number of electrons in different types of subshells.
All elements in the same block have their valence electrons in the same type of subshell.
- Subshells are in turn grouped in shells.
For the first three periods in the periodic table all elements in one period have their outermost electrons in the same shell.