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| Question | Answer |
| What does the oxidation number of an element tell you? | The total number of electrons it has donated or accepted to form an ion or to form part of a compound |
| Name the rules for oxidation numbers | 1. Uncombined elements (or elements bonded to identical atoms) have an oxidation number of 0 2. The oxidation number of a simple monatomic ion is the same as its charge 3. For molecular ions, each of the constituent atoms has an oxidation number of its own and the sum of their oxidation numbers equals the overall oxidation number 4. The sum of the oxidation numbers for a neutral compound is 0 5. Oxygen nearly always has an oxidation number of -2, EXCEPT in peroxides (O₂²⁻) where it's -1 and molecular oxygen (O₂) where it's 0 6. Hydrogen always has an oxidation number of +1, EXCEPT in metal hybrids (MHₓ) where it's -1 and in molecular hydrogen (H₂) where it's 0 |
| Complete the sentences: If an element can have multiple __________ numbers, or isn't in its 'normal' oxidation state, its oxidation number can be shown by using __________ __________. The _________ ___________ are written _______ the name of the element they correspond to. | If an element can have multiple OXIDATION numbers, or isn't in its 'normal' oxidation state, its oxidation number can be shown by using ROMAN NUMERALS. The ROMAN NUMERALS are written AFTER the name of the element they correspond to. |
| What do ions with names ending in -ate contain? | Oxygen Another element |
| What is the formula for sulphate (VI) ions? | The sulphur has oxidation number +6 The ion is SO₄²⁻ |
| What is the formula for sulphate (IV) ions? | The sulphur has oxidation number +4 The ion is SO₃²⁻ |
| What is the formula for nitrate (III) ions? | Nitrogen has oxidation number +3 The ion is NO₂⁻ |
| What is oxidation, in terms of electron transfer? | Loss of electrons (OIL) |
| What is reduction, in terms of electron transfer? | Gain in electrons (RIG) |
| What do oxidising agents do? | An oxidising agent accepts electrons and gets reduced |
| What do reducing agents do? | A reducing agent donates electrons and gets oxidised |
| When metals form compounds, what happens to the oxidation number? | When metals form compounds, they generally donate electrons to form positive ions - the oxidation number INCREASES |
| When non-metals form compounds, what happens to the oxidation number? | When non-metals form compounds, they generally gain electrons and form negative ions - the oxidation number DECREASES |
| What happens during a redox reaction? | Something is oxidised (loses electrons) and something is reduced (gains electrons) |
| TRUE OR FALSE: The reaction between acids and metals is a redox reaction | TRUE The metal atoms are oxidised to form positive metal ions (in salts). The hydrogen ions in solution are reduced, forming hydrogen molecules |
| In the following reaction, which compound is oxidised and which compound is reduced? 2K + H₂SO₄ --> K₂SO₄ + H₂ |
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