Predict properties of Group 1 elements from trends down the group.

Group 1 elements, known as alkali metals, exhibit similar properties due to their single outer-shell electron. As you move down the group, the reactivity increases because the outer electron is further from the nucleus, making it easier to lose. This trend results in lower melting and boiling points, as well as increased reactivity with water and halogens. For example, lithium reacts less vigorously with water compared to potassium, which reacts explosively. Understanding these trends allows predictions about the behavior of these elements in chemical reactions.