Which is more reactive between sodium and potassium?
Due to both potassium and sodium possessing one electron in their outer shell, they are both Group 1 elements. The reactivity of this group increases as you go down as the atoms become larger, and the outer electron will move further away from the nucleus and the force of attraction between the outer electron decreases and nucleus. As potassium is larger than sodium, potassium's electron is further away from the nucleus thus, the outer electron is lost easier. This requires less energy and therefore can be said to be more reactive.
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