Covalent Bonding: It is the strong electrostatic force of attraction between a shared pair of
electrons and the nuclei of the bonded atoms. Covalent bonding occurs between non- metallic
elements and polyatomic ions.
• Orbital Overlap: A covalent bond is the overlap of atomic orbitals. The bonded atoms often have
same electronic structure as nearest noble gas.
• Attraction: Attraction is localised as attraction acts solely between shared pair of electrons and
nuclei of bonded atoms unlike ionic.
• Lone Pairs: Show lone pairs when drawing- an outer shell pair of electrons that is not involved in
chemical bonding.
• Carbon forms 4 bonds. Nitrogen forms 3. Oxygen forms 2. Hydrogen forms 1.
• Boron: It has three outer- shell electrons. Forms covalent compounds like BF3 which has six
electrons in the outer shell altogether and not eight.
• Phosphorus, Sulphur and Chlorine: Phosphorus has five outer- shell electrons and can form PF3
and PF5. Sulphur can form SF2, SF4 and SF6. Chlorine can form ClF, ClF3, ClF5 and ClF7.
• Expansion of the Octet: All three above are in Period 3, n=3, so can hold maximum of 18 electrons.
It called expansion of the octet and only possible from the n=3 shell- the d sub shell.
• Can arrange their electrons differently by having some electrons as single and some as lone pairs.
• Dative Covalent: Aka coordinate bond. It is a covalent bond in which both pair of electrons has
been donated by one of the atoms. The shared pair of electrons was originally a lone pair of
electrons on one of the bonded atoms. A dative covalent bond shown by a → in displayed formula.
• Use normal stuff first and if that doesn’t work, use Dative and n=3 holds 18e- as last resort to make
stable compound.
• Multiple Covalent Bond: In double covalent, electrostatic force of attraction between two shared
pairs of electrons and the nuclei of bonded atoms.
• If stuck drawing compound, start drawing dot and cross diagrams from different element.
• Average Bond Enthalpy: The larger the value of this, the stronger the covalent bond.
