Atoms, Elements, and Compounds: Bonding and Structures

Ions and Ionic Bonds

• Ion Formation: Cations are positive ions, and anions are negative ions.
• Ionic Bond Definition: Strong electrostatic attraction between oppositely charged ions, formed between metallic and non-metallic elements.
• Structure: Giant lattice structure consisting of a regular arrangement of alternating positive and negative ions.
• Properties:
  • High melting points and boiling points.
  • Good electrical conductivity when aqueous or molten; poor electrical conductivity when solid.

Simple Molecules and Covalent Bonds

• Covalent Bond Definition: Formed when a pair of electrons is shared between two atoms, resulting in noble gas electronic configurations.
• Molecules: Dot-and-cross diagrams represent bonding in molecules including $H_2$, $Cl_2$, $H_2O$, $CH_4$, $NH_3$, $HCl$, $CH_3OH$, $C_2H_4$, $O_2$, $CO_2$, and $N_2$.
• Properties:
  • Low melting points and boiling points due to weak intermolecular forces.
  • Poor electrical conductivity.

Giant Covalent Structures

• Key Substances: Graphite, diamond, and silicon (IV) oxide ($SiO_2$).
• Structure-Property Uses:
  • Graphite: Used as a lubricant and as an electrode.
  • Diamond: Used in cutting tools.
• Structural Similarities: Diamond and silicon (IV) oxide ($SiO_2$) display similar properties related to their giant covalent structures.

Metallic Bonding

• Metallic Bond Definition: Electrostatic attraction between positive ions in a giant metallic lattice and a 'sea' of delocalised electrons.
• Properties:
  • Good electrical conductivity.
  • Malleable and ductile.