WebElements Periodic Table » Sodium » properties of free atoms
2.1 Atoms, Isotopes, Ions, and Molecules: The Building Blocks | TEKS Guide
Octet Rule: Why Are Atoms With 8 Valence Electrons So Stable?
Chemical Bonding
Hydrogen emission spectrum spectroscopy successive ionisation energy patterns related to sub-shells and group of periodic table GCE A Level revision notes