Group 2, the alkaline earth metals revision notes

Group 2: The Alkaline Earth Metals

Trends in Atomic Radius and First Ionisation Energy

As you move down Group 2, the atomic radius increases due to the addition of electron shells. This increase in distance between the nucleus and the outer electrons results in a decrease in the effective nuclear charge felt by these outer electrons, leading to a lower first ionisation energy.

Reactivity Trends

Reactivity increases down the group. This is due to the decreasing ionisation energy, making it easier for the atoms to lose their outermost electron. For example, magnesium reacts with water slowly, while barium reacts vigorously.

Reactions with Oxygen, Water, and Acids

• Oxygen: Group 2 metals react with oxygen to form metal oxides. For instance, magnesium burns in air to produce magnesium oxide.
• Water: Reactivity with water varies; beryllium does not react, while barium reacts vigorously, producing hydrogen gas and hydroxides.
• Acids: Group 2 metals react with dilute acids to produce hydrogen gas and corresponding metal salts.

Solubility Trends

The solubility of Group 2 hydroxides increases down the group, making barium hydroxide highly soluble, while sulfates show the opposite trend, with barium sulfate being insoluble.

Medical Applications of Barium Sulfate

Despite the toxicity of many barium compounds, barium sulfate is safe for medical use as it is insoluble and does not enter the bloodstream, making it useful for X-ray imaging of the digestive system.

Uses of Magnesium Hydroxide and Calcium Carbonate

Magnesium hydroxide is used as an antacid to neutralize stomach acid, while calcium carbonate is commonly used in antacids and as a calcium supplement.