Covalent Bonding and Summary

when two or more non-metal atoms react together, they ened to gain electrons to reach full shells- can only manage this by sharing electronsin diagrams only outer shells are shown

two hydrogen atoms share one electron eachbonded atoms form a molecule

ionic bonding = metal and non-metal bondingcovalent bonding = non-metals bonding

Diatomic MoleculesBr, I, N, Cl, H, O, F(Brinklehoff)Bromine, Iodine, Nitrogen, Chlorine, Hydrogen, Oxygen, Fluorine

double covalent bond: when atoms are sharing two pairs of electrons

In molecular compounds, atoms of different elements share electrons with each other- called covalent compounds (covalent bonds)

Examples:- water (H2O)- ammonia- methane

mus

must have two electrons in a single covalent bond

Properties of Ionic Compounds:- usually solids at room temperature- high melting points --> strong electrostatic forces holding the crystal lattice together- a lot of energy is needed to separate the ions and melt the substance- usually hard substances- usually cannot conduct electricity- usually cannot conduct electricity when solid (ions are not free to move)- dissolve in water (atoms of water bond with positive and negative and break the bonds)- conduct electricity when in the molten state or in aqueous solution (forces of attraction between ions are weakened)- not volatile

Properties of Covalent Compounds: - - low melting and boiling points- weak intermolecular forces of attraction which exist between simple molecules- giant molecular substances have higher melting points (strong covalent bonds)- do not conduct electricity in molten state or dissolved in water- do not contain ions- some moleculles react with water to produce ions (hydrogen chloride + water = hydrogen and chloride ions- generally do not dissolve in water- more volatile

Volatility = measure of the tendency of a substance to vaporize- low boiling point

Sili

Silicon dioxideDiamondGraphite

atoms are joined together by covalent bonds in a massive network

Simple molecular structures are:- simple- formed from only a few atoms- strong covalent bonds between atoms with a molecule (intramolecular bonds)- weak bonds between molecules (intermolecular bonds_

SiO2 is a giant structure where each silicon atom forms covalent bonds with four oxygen atomseach oxygen atom has two bonds

Definition: different physical forms of the same element

Graphite: only 3 of the electrons in its outer shell are covalently bonded- one delocalised (spare) electron makes electron clouds between the layers of other electrons = conducts electricity- layers have weak forces of attraction = pass over each other easily

Diamond:- four strong covalent bonds = does not conduct electricity, has a high melting point, is the hardest known substance- giant covalent structure

mono = 1dio - 2tri = 3tetra = 4Mass = molar mass/number of moles

Covalent Bonding

Covalent Compounds

Giant Covalent Structure - macromolecular

Allotropes

Summary