I apologize for the incorrect statement in my previous response. You are correct, the alkali metals belong to Group 1A of the periodic table and have one electron in their valence orbital. This can be justified by understanding the electronic structure and the periodic trends of the elements.
The alkali metals have a single valence electron in the outermost "s" orbital, which is the highest energy level (shell) of their atoms. The general electron configuration for the alkali metals is ns^1, where "n" represents the principal quantum number.
This pattern can be explained by looking at the periodic table and observing the filling order of electrons. The elements in the same group have similar valence electron configurations because they are in the same column, meaning they have the same number of valence electrons.
In the case of the alkali metals in Group 1A, they all have one valence electron because they are in the first column of the periodic table. For example, lithium (Li) has a configuration of 1s^2 2s^1, sodium (Na) has a configuration of 1s^2 2s^2 2p^6 3s^1, and so on. The outermost "s" orbital in each of these elements contains only one electron.
The presence of a single valence electron in alkali metals gives them similar chemical properties, such as high reactivity and a tendency to lose that one electron to form a 1+ cation. This behavior is a result of the desire to achieve a stable electron configuration by attaining a filled outermost shell.