Compare the metallic and non-metallic behaviours of elements, including group trends and the reactivity for the alkali metals (Li–Cs) and the halogens (F–I).

Sodium (Na) reacts vigorously with chlorine (Cl₂) to form sodium chloride (NaCl). Rubidium (Rb) also reacts with chlorine under the same conditions. Which statement best compares the reactivity and product properties of these two reactions?

A student places a small piece of lithium into a beaker of water and observes a steady reaction with fizzing. The student then places a small piece of caesium (of similar mass) into another beaker of water. Compare the reactivity of caesium with that of lithium, and explain the difference in terms of periodic trends.