Chemistry topic 3 bonding

What is an ionic bond?

The electrostatic attraction between oppositely charged ions

What is an ionic lattice?

A giant, regular, three-dimensional arrangement of oppositely charged ions, with strong electrostatic attractions acting in all directions.

Explain the properties of ionic compounds.

• High melting/boiling points: much energy is needed to overcome strong electrostatic attractions between oppositely charged ions.

• Solubility: many dissolve in water because polar water molecules attract and separate the ions.

• Conductivity: conduct when molten or dissolved because ions can move and carry charge. Solid ions are fixed, so cannot conduct.

Define a covalent bond and a dative covalent bond.

• Covalent bond: strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

• Dative covalent bond: a covalent bond in which both shared electrons are donated by the same atom.

How do you draw dative dot-and-cross diagrams?

How do you draw triple dot-and-cross diagrams?

What is metallic bonding? What do sodium and magnesium diagrams show?

Metallic bonding: strong electrostatic attraction between positive metal ions and delocalised electrons.

• Sodium: regular arrangement of Na⁺ ions, with one delocalised electron per atom.

• Magnesium: regular arrangement of Mg²⁺ ions, with two delocalised electrons per atom.

Explain metals’ melting/boiling points and electrical conductivity.

• Generally high melting/boiling points: much energy is needed to overcome strong attractions between positive ions and delocalised electrons.

• Conduct when solid or molten: delocalised electrons move and carry charge.

Explain giant covalent structures and their properties.

A giant network of atoms joined by strong covalent bonds.

• High melting/boiling points: much energy is needed to break many strong covalent bonds.

• Generally do not conduct: no delocalised electrons.

• Graphite and graphene conduct: they have mobile delocalised electrons.

Explain simple molecular substances and their properties.

Separate molecules with strong covalent bonds within molecules and weak intermolecular forces between molecules.

• Low melting/boiling points: little energy is needed to overcome weak intermolecular forces. Covalent bonds remain intact.

• Solubility: non-polar molecules generally dissolve in non-polar solvents; some polar molecules dissolve in water.

• Generally do not conduct: no mobile ions or delocalised electrons.