Chemical Bonding

Covalent BondsIs the sharing of electrons between the nuclei of atoms.Form between atoms of non-metalsCovalent bonds form when electrons are shared between two atoms.Covalently bonded substances is called a molecule.Single covalent bondsForms when each atom shares one electron and attains a noble gas structure.Double covalent bondsInvolves two pairs of electrons.Triple covalent bondsForms when there are three shared pairs of electronsWe can represent covalent bonds by using the Cooper structure or the Lewis structureRelative molecular mass of a covalent compoundThe relative molecular mass(Mr) is equal to the sum of all the relative atomic masses of the atoms present in the molecule.E.g. calculate relative molecular mass of ammonia (NH3)Mr(NH3)= Ar(N) + 3Ar(H)             =14,0 + (3 X 1,01)             =17,03

Ionic BondingIonic bonds are form between a metal to a non- metal.Electrons are transferred forming ions.These exert an electrostatic force of attraction on each other.Formation of ionic bondsIons are formed by the loss or gain of electrons.When an atom forms an ion, the electron structure becomes that of the noble gas closest to it.Ions tend to be stable like noble gasses and do not react with other molecules.Formation of an ionic crystal latticeFormation of positive ions are always coupled with the formation of negative ions.Metal lose electrons forming positive ions, non-metals gain these electrons forming negative ions.The positive metal ions then attract the negative non-metal ions forming ionic bonds.Ion PairsA pair of ions that bond do not form a molecule but an ion pair.They form compounds made up of ion-pairs.Ionic Bonds between metal atoms and compound ionsCompound or polyatomic ions form  stable groups of atoms which carry a charge.Groups of atoms as a whole acts as charged particles in forming an ionic compound with an oppositely charged ion.Relative Formula Mass of an ionic compoundThe relative formula mass is equal to the sum of the relative atomic masses of atoms in the chemical formula.****Just add all the relative atomic masses for the atoms that make up formula of compound*****E.g. calculate relative formula mass of aluminum sulfide (Al2S3)

Metallic Bondingformed when a delocalized electron is shared among positive ions in a metal.Bonding in MetalsAtoms from the same metals form metallic bonds.The valence electrons become detached from the atom and roam freely through the metal. Atoms become positive ions as electrons move away causing a net deficiency of electrons around each atom.By saying the valence electrons are delocalized means that they belong to positive ions in the metal lattice.No valence electrons belong to a specific atom.Metals form giant structures of many metal atoms as the electrons and positive ions have strong attractive forces between them.Metallic bonds and properties of metals1) Conduction of heat and electricity2) Malleability and ductility 3) High density4) Metallic lusterAlloysFormed when different metals are melted and mixed.This includes:1) Stainless steel2) Brass3) Sterling silver

Covalent bonding

Ionic bonding

Metalic bonding