What are Metals that are less reactive than alkali metals and alkaline-earth metals called

Transition metals are less reactive than alkali metals because of their high ionization potential and high melting point.

On moving from left to right of the periodic table for every period, electrons fill in the same shell or orbital, with the alkali metals having the least filled outermost shells, one electron, which equates to fewer protons in them.

Consequently, they have a lesser attraction power from the nucleus, whereas, the corresponding transition metals of the same period have more protons interacting with electrons at the same distance, far from the nucleus as the alkali metals.

The first ionization energies (I1) of the alkaline earth metals are not as low as the alkali metals. The alkaline earth metals are therefore less reactive than the alkali metals (Be and Mg are the least reactive of the alkaline earth metals). Several physical properties of these elements are compared in Table 7.7.

it means there are 3 atoms of oxygen

it is the most commonly accepted one