AQA GCSE FOUNDATION Chemistry: Group 1 - Alkali Metals

AQA GCSE Foundation Chemistry: Group 1 - Alkali Metals

Introduction

Group 1 of the periodic table contains the alkali metals: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs) and francium (Fr). These elements share similar properties due to their electron configurations and are highly reactive metals.

Properties of Alkali Metals

• Metallic Bonding: Alkali metals have a single valence electron in their outermost shell. This electron is loosely held and readily participates in metallic bonding, resulting in soft, silvery-white metals with low melting and boiling points.
• Reactivity: Alkali metals are highly reactive due to their tendency to lose their single valence electron, forming a +1 ion. This makes them strong reducing agents.
• Reaction with Water: Alkali metals react vigorously with water, producing hydrogen gas and a metal hydroxide. The reaction becomes more vigorous as you move down the group. For example, lithium reacts slowly, sodium reacts vigorously, and potassium reacts explosively.
• Reaction with Oxygen: Alkali metals react with oxygen in the air to form oxides. The oxides are basic in nature.
• Reaction with Halogens: Alkali metals react with halogens to form ionic salts.

Reactivity Trends within Group 1

As you move down Group 1, the reactivity of the alkali metals increases. This is due to the following reasons:

• Atomic Radius: Atomic radius increases down the group. This means the valence electron is further from the nucleus and is held less tightly, making it easier to lose.
• Shielding Effect: The increasing number of electron shells between the valence electron and the nucleus increases the shielding effect, further reducing the attraction between the nucleus and the valence electron.
• Ionisation Energy: Ionisation energy decreases down the group. This is the energy required to remove one electron from an atom. Lower ionisation energy indicates easier electron removal, leading to higher reactivity.

Summary

Alkali metals are highly reactive metals with distinctive properties. Their reactivity increases as you move down the group due to increasing atomic radius, shielding effect, and decreasing ionisation energy.