Assessment and Qualifications Alliance (AQA) GCSE Chemistry Paper 1 Practice Exam

As you move down Group 1 of the periodic table, the reactivity of the metals increases. This trend is primarily due to the structure of the atoms as you progress down the group.

Group 1 metals, also known as alkali metals, have one electron in their outermost shell. This single electron is relatively easy to lose, and the reactivity is linked to how readily the atom can lose this outer electron to form positive ions. As you go down the group, the number of electron shells increases. For instance, lithium has only two shells, while cesium has six. This results in the outermost electron being further away from the nucleus, which decreases the attractive force experienced by this electron due to increased distance and shielding by the inner electrons.

As a result, the outer electron can be removed more easily in lower Group 1 metals, leading to increased reactivity. Therefore, the correct answer highlights this trend of increasing reactivity as you move down the group. The other options do not accurately reflect this observed pattern.