Summary
The elements of Groups 1 and 2 show distinct trends in ionization energy, reactivity, and solubility. Group 1 and 2 metals react with oxygen, water, and acids to form oxides, hydroxides, and salts, respectively.
- Ionisation Energy — the energy required to remove an electron from an atom. Example: First ionization energy is the energy needed to remove one electron from a neutral atom.
- Reactivity with Water — how metals react with water to form hydroxides and hydrogen gas. Example: Calcium reacts vigorously with water to form calcium hydroxide and hydrogen gas.
- Thermal Stability — the resistance of a compound to decomposition when heated. Example: Magnesium nitrate decomposes more easily than calcium nitrate.
- Solubility Trends — the ability of a substance to dissolve in water. Example: The solubility of Group 2 hydroxides increases down the group.
Exam Tips
Key Definitions to Remember
- Ionisation energy
- Reactivity with water
- Thermal stability
- Solubility trends
Common Confusions
- Confusing the reactivity trends of Group 1 and Group 2 elements
- Misunderstanding the difference between ionization energy and reactivity
Typical Exam Questions
- What happens when magnesium reacts with water? Magnesium reacts slowly with water to form magnesium hydroxide and hydrogen gas.
- How does ionization energy change across a period? Ionization energy generally increases across a period.
- Why does the solubility of Group 2 sulfates decrease down the group? Due to increasing lattice energy and decreasing hydration energy.
What Examiners Usually Test
- Trends in ionization energy and reactivity
- Reactions of metals with water, oxygen, and acids
- Solubility and thermal stability trends in Group 2 elements
