Learn: Group 1 Alkali Metals and Trends in Reactivity

Welcome!Great to see you back! You've already learned about the periodic table, electronic structure, and the properties of metals. Today, we'll focus on Group 1 elements, also known as the alkali metals

What are Group 1 Alkali Metals?Group 1 elements are metals found on the leftmost column of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). These metals are highly reactive and share common properties, such as reacting with water and forming alkaline solutions.

Properties of Alkali MetalsAll Group 1 metals are soft and can be cut with a knife. They have low density, with some being light enough to float on water. They all have one electron in their outer shell, which makes them very reactive.

Trends in ReactivityAs you move down Group 1, the metals become more reactive. This is because the outer electron gets further away from the nucleus, making it easier to lose during reactions. This increased reactivity is why sodium is more reactive than lithium, and potassium is even more reactive than sodium.

Reactions with WaterAlkali metals react with water to produce hydrogen gas and an alkaline solution of a metal hydroxide. For example, sodium reacts with water to form sodium hydroxide and hydrogen gas. The reaction becomes more vigorous as you move down the group.

Observing the ReactionWhen an alkali metal reacts with water, you may see fizzing as hydrogen gas is produced. Larger alkali metals like potassium and rubidium may react very vigorously, even causing explosions. This shows how reactivity increases as you move down Group 1.

Trends in Physical PropertiesAs you move down Group 1, the metals become softer and their melting and boiling points decrease. This is because the metallic bonds become weaker as the atoms get larger.

Review Time!Great work! You've learned about the properties and reactivity of Group 1 alkali metals. Let's test your understanding with a few final questions.