PolarityBonds and molecules

Types of bonds

Ionic bonds occur when an atom of low ionisation energy loses valence electrons to an

atom of high ionisation energy.

Types of bonds

Covalent bonds occur when atoms of similar ionisation

energies share valence electrons.

Types of bonds

Ionisation energy is the energy required to

remove loosely held valence electrons from an atom. A similar property is how well atoms attract or hold electrons when

bonding.

Types of bondsThe name given to this electron attracting ability of atoms is electronegativity.

Types of bonds

Types of bondsA very large difference in electronegativities between atoms in a bond will produce an ionic bond. A small difference produces a covalent bond.

Types of bondsIf the atoms in a covalent bond have identical electronegativities then they will share the electrons equally.

Types of bondsNeither end of the bond will be more negative than the other. This symmetrical bond is known as a non-polar bond.

Types of bonds

If two atoms bond with slightly different electronegativities then one atom will have an uneven share of the electrons.

Types of bondsThis unsymmetrical bond will have one end which is more negative than the other due to the electrons spending more time there.

Types of bondsThis bond is said to have a dipole since each end is different. It is called a polar bond.

eg hydrogen fluoride

Types of molecules

The previous examples of molecules were diatomic. There is only one bond in each. If the bond is polar then the molecule is polar.

Types of molecules

If the bond is non polar then the molecule is also non-polar. eg Cl2

Types of molecules

If a molecule has more than one line of symmetry it will be non-polar.

Types of molecules

eg BF3, CCl4, CO2

Types of molecules

If a molecule has only one line of symmetry it will be polar.

Types of molecules

CHCl3, NH3, H2O

shape and polarity influence the chemical and physical properties

Types of molecules