Chemistry Unit 1

Unit 1.1: Formula and equations

Formula of compounds and ions

Oxidation numbers – is the number of electrons that need to be added (or taken away) from an element to make it neutral.

Rules – a substance is oxidised with an increase in oxidation numbers

• Oxidation number of chlorine = -1 (except combined with oxygen/fluorides)
• Group 1= +1
• Group 2 = +2
• Group 3 = +3
• Group 7 = -1

Oxidation and Reduction

Oxidation - involves the lo** of electrons or hydrogen OR gain of oxygen OR increase in oxidation state

Reduction- involves the gain of electrons or hydrogen OR lo** of oxygen OR decrease in oxidation state

Oxidising agent – removes electrons from something else and will be reduced (non-metals)

Reducing agent – gives electrons to something else and will be oxidised (metals)

 Example of an Oxidation Reduction Reaction

Balance the following redoxreaction in an acidic solution:

Cu(s) + HNO₃(aq) → Cu²⁺(aq) + NO(g)

Step 1: Identify what is being oxidized and what is being reduced. (a**ign oxidation states to each atom)

Step 2: Break the reaction into twohalf reactions: oxidation and reduction.

Oxidation: Cu → Cu²⁺

Reduction: HNO₃ → NO

Step 3: Balance each half-reaction by both…