Periodic trends
Non-metals are on the right side of the periodic table, and metals are on the left. If you go down a period of metals (but not the transition metals) they become more reactive (this is because there are more electron shells so since metals lose electrons the more electron shells they have, the weaker the bond is between the positive nucleus and the valency electrons, so the more easily it is lost.) With non-metals, going down a period, the non-metal becomes less reactive (the reason is the opposite than for metals).