Summary
Group 2 metals, from magnesium to barium, show trends in reactivity and solubility as you move down the group. They react with oxygen, water, and acids to form oxides, hydroxides, and salts, with increasing reactivity down the group.
- Reactivity with Oxygen — Group 2 metals burn in oxygen to form metal oxides. Example: Magnesium burns in oxygen to form magnesium oxide (MgO).
- Reactivity with Water — Group 2 metals react with water to form metal hydroxides and hydrogen gas. Example: Calcium reacts vigorously with water to form calcium hydroxide (Ca(OH)2) and hydrogen gas.
- Reactivity with Acids — Group 2 metals react with acids to form salts and hydrogen gas. Example: Barium reacts with hydrochloric acid to form barium chloride (BaCl2) and hydrogen gas.
- Thermal Stability — The thermal stability of nitrates and carbonates increases down the group. Example: Calcium nitrate requires more energy to decompose than magnesium nitrate.
- Solubility Trends — The solubility of hydroxides increases, while the solubility of sulfates decreases down the group. Example: Barium sulfate is less soluble in water than magnesium sulfate.
Exam Tips
Key Definitions to Remember
- Reactivity with oxygen: Formation of metal oxides
- Reactivity with water: Formation of metal hydroxides and hydrogen gas
- Thermal stability: Resistance to decomposition upon heating
Common Confusions
- Confusing the solubility trends of hydroxides and sulfates
- Misunderstanding the increase in reactivity down the group
Typical Exam Questions
- How does magnesium react with water? Magnesium reacts slowly with cold water to form magnesium hydroxide and hydrogen gas.
- What happens when calcium reacts with hydrochloric acid? Calcium reacts with hydrochloric acid to form calcium chloride and hydrogen gas.
- Why does the solubility of sulfates decrease down the group? Due to the increase in lattice energy and decrease in hydration energy.
What Examiners Usually Test
- Trends in reactivity and solubility of Group 2 elements
- Reactions of Group 2 metals with water, oxygen, and acids
- Explanation of thermal stability trends in nitrates and carbonates