Amphoteric Metals
Certain metals like Aluminium (Al) and Zinc (Zn) are amphoteric, meaning they react with both acids and bases. This dual behaviour makes them unique among metallic elements.
Oxidation
Oxidation involves the gain of oxygen, loss of electrons, and an increase in oxidation number.
- The substance that causes oxidation is called the oxidising agent.
- Example: Acidified Potassium Dichromate (K₂Cr₂O₇) acts as a reducing agent; it turns orange to green when reduced.
Reduction
Reduction is the loss of oxygen, gain of electrons, and a decrease in oxidation number.
- The substance that causes reduction is called the reducing agent.
- Example: Acidified Potassium Permanganate (KMnO₄) acts as an oxidising agent; it changes from pink/purple to colourless when reduced.
Group 1: Alkali Metals
Reactivity, density, and softness increase down the group, while melting and boiling points decrease. These metals react vigorously with water, oxygen, and chlorine, forming cations.
Group 2: Alkaline Earth Metals
These metals are less reactive than Group 1 but still form basic oxides and cations. Their reactivity increases down the group.
Group 7: Halogens
Reactivity decreases down the group, while boiling point, melting point, and density increase. Halogens form anions and exist as diatomic molecules (Cl₂, Br₂, I₂).
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