The
electron configuration for an atom indicates the principal energy levels and subshells which are occupied for that atom.
For an atom in the ground state the available electrons (equal to the atomic number) occupy subshells of lowest possible energy.The relative energies of the subshells up to the fourth energy level are: 1s
The maximum number of electrons per subshell is:
- s-subshell--one orbital therefore two electrons maximum
- p-subshell--three orbitals therefore six electrons maximum
(filled singly until all are half occupied) - d-subhsell--ten orbitals therefore ten electrons maximum
(filled singly until all are half occupied)
The
valence electrons involved in chemical bonding are in the outermost energy level.
The periodic table can be divided be into blocks depending on the subshell in which the valence electrons are located.
s - (Groups 1 and 2), p - (Groups 13-18), and d - (Groups 3-12) blocks