Why are transition metals less reactive than alkali metals?

Transition metals are less reactive than alkali metals due to their higher ionisation energies and more stable electron configurations.

Transition metals, found in the middle of the periodic table, are less reactive than alkali metals, which are located in the first group of the table. This difference in reactivity can be attributed to their atomic structure, specifically their electron configurations and ionisation energies.

Alkali metals have one electron in their outermost energy level, which is relatively far from the nucleus and therefore weakly held. This makes it easy for alkali metals to lose this electron and form a positive ion, a process that is often associated with chemical reactivity. In contrast, transition metals have more electrons in their outer energy levels, which are closer to the nucleus and more strongly held. This makes it harder for transition metals to lose these electrons and become ions, resulting in lower reactivity.

Furthermore, transition metals have what is known as 'd-block' electron configurations. This means they have partially filled d-orbitals that can accept electrons from other atoms, making them more stable and less likely to react. Alkali metals, on the other hand, do not have this stability and are therefore more reactive.

The ionisation energy, or the energy required to remove an electron from an atom, is also a factor. Transition metals generally have higher ionisation energies than alkali metals, meaning it requires more energy to remove an electron from a transition metal atom. This higher energy requirement contributes to their lower reactivity.

In summary, the lower reactivity of transition metals compared to alkali metals is due to their more stable electron configurations and higher ionisation energies, which make them less likely to lose electrons and react with other substances.