The most reactive and active elements in the periodic table are found in the first two groups: Alkali Metals and Alkaline Earth Metals.
Group 1 (Alkali Metals) consists of elements:
lithium (Li) 3
sodium (Na) 11
potassium (K) 19
rubidium (Rb) 37
caesium (Cs) 55
francium (Fr) 87
Group 2 (Alkaline Earth Metals) consists of elements:
beryllium (Be) 4
magnesium (Mg) 12
calcium (Ca) 20
strontium (Sr) 38
barium (Ba) 56
radium (Ra)88
According to the New World Encyclopedia, alkali metals all have one valence electron which is easily lost to form an ion with a single positive charge. They have the lowest ionization energies in their respective periods. This makes them very reactive and they are the most active metals.
Alkaline earth metals on the other hand all have two valence electrons and tend to lose both to form ions with a two plus charge. Berylium is the least metallic element in the group and tends form covalent bonds in its compounds. These metals are less active than the alkali metals, but are still fairly active.
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