Gcse chemistry unit 2 AQA

Chemistry

Structure and bonding

Types of bonding:

• Ionic
• Covalent
• Metallic

Ion formation

• Ions are formed by the transfer of electrons between atoms, this results in charged particles.
• Atoms that gain electrons become negatively charged
• Atoms that lose electrons become postively charged
• This occurs between metal and non-metal elements

Ionic bonding

• Sodium metal loses an electron and becomes postively charged
• Chlorine (non- metal) gains an electron and becomes negatively charged.

There are strong electrostatic attraction between oppositely charged ions

Giant ionic structure

• High melting point
• Conducts electricity when molten or in solutions (ions are free to move)

Metallic bonding

Regular layers of ions are able to slide over each other. Strong electrostatic attraction between the ions and delocalised electrons allow the metal to be malleable and ductile

• It is a layer of ions
• The outer layers may sometimes contain delocalised electrons, which can carry currents
• It is the strong electrostatic attraction between the positively chared ions and the negative sea of electrons that hold the structure together.

Giant metallic structure: Have high melting points and conduct electricity when solid or molten.

Covalent bonding

• Covalent bonds are formed when atoms share electrons
• This occurs between non-metal elements

Diamond

• All carbon atoms are joined to 4 others with strong covalent bonds
• It is a giant covalent structure (high melting point, does not conduct electricity)
• Hard

Diamond is hard because of its giant covalent structure. All of the carbon atoms are joined to 4 others with strong covalent bonds. This means that a lot of energy is needed to break them apart. However due to this, there are no delocalised electrons, which means that diamond can't conduct electricity.

Graphite

• Layers of carbon atoms in which each carbon atom is joined to 3 others by strong covalent bonds.
• There is a sea of delocalised electrons (can carry a current)
• The layers are held together by weak forces to the layers of atoms can slide across each other.
• Giant covalent structure.

Graphite has a giant covalent structure. Each carbon atom is joined together to 3 others. Graphite is layered. Due to the weak forces that bind these layers together, the atoms on each layers can slide. It also has a sea of electrons, which…