Based on the information provided about lithium, we can predict the following properties for rubidium and cesium:

• Rubidium (Rb): Rubidium is expected to be a solid at room temperature, similar to lithium. It will be more reactive than lithium, and therefore less soft. It will react with water, although the reaction will be faster than that of lithium. Rubidium is a soft, silvery-white metal.
• Cesium (Cs): Cesium is expected to be a solid at room temperature and will be even more reactive than rubidium. It will react vigorously with water, producing hydrogen gas and cesium hydroxide. Cesium is a soft, silvery-white metal and is the most reactive of the alkali metals.

Comparison to Lithium: Rubidium and cesium will be more reactive than lithium. They will be less soft than lithium. Their reactivity with water will be greater than that of lithium. They will also be more likely to tarnish in air than lithium.

Based on the reactivity of sodium, we can predict the following properties for potassium, calcium, and magnesium:

• Potassium (K): Potassium is expected to be even more reactive than sodium. It will also react vigorously with water, producing hydrogen gas and potassium hydroxide. Potassium is a soft, silvery-white metal and is also highly reactive with air, tarnishing quickly. It is more reactive than calcium and magnesium.
• Calcium (Ca): Calcium is expected to be less reactive than sodium but more reactive than magnesium. It will react with water, although the reaction will be slower than that of sodium. Calcium is a strong, white metal. It reacts with acids and is used in various applications, including in the human body.
• Magnesium (Mg): Magnesium is expected to be less reactive than calcium. It will react with water, but the reaction will be relatively slow. Magnesium is a lightweight, silvery-white metal. It is often used in alloys and is also used in fireworks.

Key Prediction: As you move down Group I, reactivity with water increases. Appearance tends to remain silvery-white, but reactivity decreases.

Based on the reaction of sodium hydroxide with hydrochloric acid, we can predict the following properties for lithium hydroxide and strontium hydroxide:

• Lithium Hydroxide (LiOH): Lithium hydroxide is expected to be soluble in water and will react with hydrochloric acid to produce lithium chloride and water. It will be less soluble and less reactive than sodium hydroxide.
• Strontium Hydroxide (Sr(OH)₂): Strontium hydroxide is expected to be soluble in water and will react with hydrochloric acid to produce strontium chloride and water. It will be less soluble and less reactive than sodium hydroxide. Strontium hydroxide is also expected to be less soluble than lithium hydroxide.

Prediction of Solubility and Reactivity: As you move down Group I, the solubility of the hydroxides generally increases. The reactivity with acids will also increase, although strontium hydroxide will be less reactive than sodium hydroxide due to the increasing ionic size and decreasing charge density of the cations.