Properties of Alkali and Alkaline Earth Metals
Group I elements, known as alkali metals, include lithium, sodium, potassium, rubidium, cesium, and francium. They are characterized by:
- Softness: They can be cut with a knife.
- Reactivity: They react vigorously with water, producing hydrogen gas and hydroxides.
- Low density: Most are less dense than water.
- Flame colors: They produce distinct flame colors when burned (e.g., sodium gives a yellow flame).
Group II elements, known as alkaline earth metals, include beryllium, magnesium, calcium, strontium, barium, and radium. Their properties include:
- Hardness: They are harder than alkali metals.
- Reactivity: They react with water, but less vigorously than alkali metals.
- Higher melting points: They have higher melting and boiling points compared to alkali metals.
- Formation of oxides: They readily form oxides and hydroxides that are less soluble than those of alkali metals.
Key points to remember
- Alkali metals are soft and highly reactive with water.
- Alkaline earth metals are harder and less reactive than alkali metals.
- Alkali metals produce distinct flame colors when burned.
- Alkaline earth metals form less soluble hydroxides.
- Both groups form oxides readily.
Worked example
Describe two properties of alkali metals and two properties of alkaline earth metals.
- Alkali metals are soft and highly reactive with water.
- Alkaline earth metals are harder and have higher melting points.