Covalent

• at least 2 electrons (non-metals) create a covalent molecule which represents the smallest unit of a chemical compund
• these molecules exist with lone pairs (valence e- unbonded) and bonding pairs (e- involved in bonding)
• lewis dot structures consist of counting the valence electrons, finding the central atom (least electronegative), drawing the bonds to the atom, putting all remaining electrons either in pairs or double bonding.
• properties of covalent compounds are its low melting and boiling point, due to weak bonding of intramolecular forces (broken apart rather than the actual molecules)
• another property of covalent compounds is the non-conductivity as there are no delocalised electrons or ions to carry the charge.
• allotropes of carbon are other covalent compounds and they include diamond, charcoal and graphite
• hydrocarbons (H and C) have an affected property and physical appearance depending on the number of bonds and carbons present.
• VSEPR stands for Valence Shell Electron Pair Repulsion.
• a tetrahedral is a shape of a molecule with 4 bonds and no pairs
• a trigonal planar molecule has 3 bonded pairs with no lone pairs on the central atom
• a trigonal pyramid are a set of lone pairs on a central atom, with 3 bonds
• a planar shaped molecule is no lone pairs on the central atom, the lone pairs on the outer atoms
• a bent molecule has 2 lone pairs on the central atom and 2 other bonds.