You are correct that there are elements like chromium (Cr), copper (Cu), niobium (Nb), molybdenum (Mo), ruthenium (Ru), platinum (Pt), and gold (Au) that have one valence electron but do not exhibit the reactivity typically associated with alkali metals. This is due to the influence of additional factors, such as electron configuration and orbital stability.
The reactivity of elements is not solely determined by the number of valence electrons but also by other factors such as the energy levels and subshells occupied by those valence electrons. Alkali metals have a single valence electron in an s-orbital, which is relatively far from the nucleus and easily lost. However, the elements you mentioned have their valence electrons in d-orbitals or higher energy levels, which have different characteristics compared to the s-orbitals.
The d-orbitals are closer to the nucleus and experience stronger electrostatic attraction, making it more difficult for the valence electrons to be readily removed. Additionally, the presence of d-orbitals in the electron configuration can provide greater stability due to the phenomenon known as half-filled or fully filled subshells.
Elements like gold and platinum have completely filled d-orbitals in their neutral states (in addition to their one valence electron). This gives them extra stability because a half-filled or fully filled d-subshell configuration is energetically favorable. As a result, these elements have less tendency to lose their valence electron and react like alkali metals.
Furthermore, the overall chemical behavior of an element is influenced by a combination of factors, including atomic size, electronegativity, and the nature of chemical bonds. These factors can vary significantly among different elements, even if they have the same number of valence electrons.
In summary, while elements like chromium, copper, niobium, molybdenum, ruthenium, platinum, and gold possess one valence electron, their reactivity is influenced by their electron configuration, the characteristics of the valence electron's orbital, and the stability associated with partially or fully filled subshells. These factors contribute to their unique chemical behavior, which differs from that of alkali metals.