What trends in reactivity are observed down a group in the periodic table?

As you move down a group in the periodic table, reactivity increases for metals and decreases for non-metals.

In the periodic table, elements are arranged into groups (vertical columns) and periods (horizontal rows). Each group contains elements with similar properties, and these properties change in a predictable way as you move down the group. For metals, which are found on the left side of the periodic table, reactivity increases as you move down a group. This is because the outermost electrons are further from the nucleus and are therefore less tightly held, making them easier to lose in a chemical reaction, which is how metals react.

For example, in Group 1 (the alkali metals), lithium at the top is less reactive than sodium below it, which in turn is less reactive than potassium. This trend continues down the group, with francium at the bottom being extremely reactive.

On the other hand, for non-metals, which are found on the right side of the periodic table, the trend is the opposite. Reactivity decreases as you move down a group. This is because non-metals react by gaining electrons to fill their outer energy level, and the further an outer electron is from the nucleus, the less attraction it feels, and the harder it is to gain an extra electron.

For instance, in Group 17 (the halogens), fluorine at the top is the most reactive element, while astatine at the bottom is the least reactive. This trend of decreasing reactivity continues down the group.

In summary, the trends in reactivity observed down a group in the periodic table are that reactivity increases for metals and decreases for non-metals. This is due to the increasing distance of the outermost electrons from the nucleus, which affects how easily these electrons can be lost or gained in a chemical reaction.