Elements with high metallic character have localized electrons in their structure. Therefore, elements with lower ionization energies are more likely to be metallic

The alkali metals have decreasing ionization energy and increasing metallic character going down the group. This means that they are increasingly reactive going down the group, as they have a greater tendency to lose their valence electron.

Reactions of Alkali Metals with Water

Alkali metals can displace H2 gas from water

The reaction releases energy; sometimes, energy released quickly enough to ignite the hydrogen gas

Reaction becomes more vigorous going down the group. This is because the valence electrons are further from the nucleus and are lost more easily.

Reaction equation

2 M(s) + 2H2O > 2 MOH (aq) + H2 (g)

Ionic Equation

2 M (s) + 2 H2O (l) > 2 M+ (aq) + 2 OH-(aq) + H2(g)

Hydroxide ions are a product of the reactions

Alkali metals make an alkaline solutions

Group 17: The Halogens

Halogens can be described based on heir non-metallic charcter, a trait is linked with electronegativity

Reaction of Halogens with Halide ons

Halogen reactivity decreases going down group 17. Fluorine is the most reactive halogen.

As electronegativity decreases, the ability of a reactant to remove electrons from another reactant decreases

Result: Higher halogens can displace lower halogens from a solution of their salts

Examples

2 KBr (aq) + Cl2 (aq) > 2 KCL (aq) + Br2 (aq)

2 KCL (aq) + I2 (aq) > No reaction

2 KI (aq) + Br 2 (aq) > 2 KBr (aq) + I2 (aq)