1. Defining the Group 1 Metals (The Exam-Centred Definition)

The **Alkali Metals** are the elements in **Group 1** of the **periodic table of elements cambridge igcse** (excluding Hydrogen). This family includes Lithium (Li), Sodium (Na), and Potassium (K)—the most commonly tested elements.

Their position in the **cambridge periodic table** in Group 1 is the key to all their properties.

Key Physical Properties (What to Write in Paper 1 & 2)

• They are **Soft Metals** (can be cut with a knife).
• They have relatively **Low Melting Points and Boiling Points** which decrease down the group.
• They have **Low Density** (Lithium, Sodium, and Potassium float on water).
• They are stored under oil to prevent reaction with **Oxygen** and **Water** in the air (a common exam question!).

2. The Critical Reactivity Trend: Down the Group

Understanding the trend in reactivity is the most high-yield topic for **Group 1** questions.

This trend is directly related to the concept of electron shielding, a core pillar in understanding the **cambridge periodic table as level** or IGCSE content.

3. Key Chemical Reactions (The Equations You Must Know)

The **alkali metals** are characterised by their vigorous reactions. You must be able to state the observations and write the balanced chemical equations.

Reaction with Cold Water

All **Group 1 metals** react vigorously with water, producing a metal hydroxide (an **alkali**) and hydrogen gas. This is a classic demonstration of their reactivity.

• Equation (General): $2M(s) + 2H_2O(l) \rightarrow 2MOH(aq) + H_2(g)$
• Example (Sodium): $2Na(s) + 2H_2O(l) \rightarrow 2NaOH(aq) + H_2(g)$
• Observations: The metal floats, melts (for Na and K), moves rapidly, fizzes (hydrogen gas), and the resulting solution turns Universal Indicator blue/purple (due to the **alkali** product, e.g., Sodium Hydroxide).

Reaction with Oxygen

When heated, **alkali metals** burn rapidly in oxygen to form metal oxides.

• Equation (General): $4M(s) + O_2(g) \rightarrow 2M_2O(s)$
• Example (Lithium): $4Li(s) + O_2(g) \rightarrow 2Li_2O(s)$ (Note: Different metals can form different oxides, but $M_2O$ is the expected IGCSE/O Level standard oxide).

4. Exam-Focused Practice and Support

To truly secure your A*, you must practice applying this knowledge, especially in practical and calculation-based papers.

Group 1 Revision Timeline

• **Step 1: Theory (Notes):** Master the reactivity trend reason (electron loss). See our Definitive Notes.
• **Step 2: Reactions (Equations):** Memorise the water reaction equation and observations.
• **Step 3: Exam Tips:** Learn how to structure your answers for 4-mark trend questions. Check the A-Grade Action Plan.