Select all the statements that correctly describe the chemical reactivity of the alkali and alkaline earth metals:

- Each alkali metal oxide has a unique numerical ratio of metal to oxygen in the chemical formula.
- In general, the alkaline earth metals are more reactive than the alkali metals.
- The alkali metals are commonly found in nature as oxides.
- The alkali metals and the alkaline earth metals are listed at the top of the chemical activity series because they are the most reactive metals.