Reactivity: Magnesium is more reactive than calcium, meaning it reacts more readily with water. This is due to differences in their atomic structures and ionization energies. Magnesium has a smaller atomic radius and a lower ionization energy than calcium, making it easier for magnesium atoms to lose electrons and form bonds with oxygen and hydrogen atoms in water.
Nature of the reaction: When magnesium reacts with water, it undergoes a chemical reaction called hydrolysis, specifically, a reaction with steam. During this process, magnesium metal combines with water molecules (H2O) to form magnesium hydroxide (Mg(OH)2) and hydrogen gas (H2). The reaction can be represented as follows:
```
Mg(s) + 2H2O(g) → Mg(OH)2(aq) + H2(g)
```
In contrast, calcium also reacts with water through hydrolysis, but its reaction is slower and less vigorous compared to magnesium. Calcium forms calcium hydroxide [Ca(OH)2] and hydrogen gas, but the reaction rate is slower due to calcium's lower reactivity.
Product formation: The products formed in the reactions of magnesium and calcium with water differ slightly. Magnesium produces magnesium hydroxide and hydrogen gas, while calcium produces calcium hydroxide and hydrogen gas. Both reactions result in the formation of metal hydroxides as the primary products, along with the evolution of hydrogen gas.
Solubility: The solubility of the metal hydroxides formed also varies. Magnesium hydroxide is insoluble in water, forming a white precipitate. In contrast, calcium hydroxide has lower solubility than magnesium hydroxide but is still considered slightly soluble in water. As a result, a cloudy suspension or a small amount of precipitate may form when calcium reacts with water.
In summary, magnesium and calcium differ in their reactivity with water. Magnesium reacts more vigorously and produces insoluble magnesium hydroxide and hydrogen gas. Calcium reacts less vigorously, forms slightly soluble calcium hydroxide, and also produces hydrogen gas.
