Final answer:
The reactivity of metals in the periodic table generally increases as you move down a group due to lower ionization energies and larger atomic radii. Transition metals, however, show varied reactivity due to their partially filled d orbitals and several other factors. Reactivity generally decreases across a period as the effective nuclear charge increases.
Step-by-step explanation:
How Reactivity of Metals Changes in the Periodic Table
The reactivity of metals tends to increase as you move down a group in the periodic table. This is because the atomic radius increases due to the addition of electron shells, positioning outer electrons further away from the nucleus, which leads to a decrease in ionization energy. Consequently, it becomes easier for these metals to lose electrons and react. Groups 1 and 2 metals, in particular, show a marked increase in reactivity as you move down the group.
For transition metals, reactivity can vary significantly. Some are very reactive, like scandium and iron, while others are nearly inert, such as the platinum metals. Transition metals have partially filled d orbitals, which affects their reactivity. Additionally, factors such as the formation of halide compounds, ability to displace hydrogen from dilute acids, and the difficulty of reducing the metal ions to the metal itself, all contribute to the varied reactivity of transition metals.
Metallic character and thus reactivity also decrease across a period as the effective nuclear charge increases, making it harder to remove an electron. The presence of an activity series helps to predict the ability of one metal to displace another in a reaction based on their relative reactivity.