On the periodic table, metals comprise much of the left hand side. The first two groups (vertical lines) are called the alkaline metals and the alkali earth metals. The group of elements in the middle part of the table are called the transition metals. The right hand side of the periodic table are the metalloids and non-metals. In general, the reactivity of metals starts as strongest on the left and decreases as you move right across the table. Metal reactivity also increases as you go from top to bottom. So the bottom left are the most reactive metals and the upper right are the least reactive. This is because metal reactivity follows the general trend for atomic radius. The smaller the atomic radius, the closer the valence electrons are to the nucleus and the harder they are to remove (ionization). The larger the atomic radius, the further away the valence electrons are from the nucleus and the easier they are to remove for reactions.