Chemistry!

001's answer is wrong. The reactivity is not descending from left to right.

In fact, the reactivity decrease from group I to group IV, then increase from group IV to group VII. Group 0 is the most unreactive.

Group II elements are quite reactive elements , but their reactivity much less than that of group I elements, since they have to lose two electrons to attain octect structure. e.g. Be does not react with water, Mg only react with steam.

Group III elements are even less reactive than group II elements, because they have to lose three electrons to attain an octect structure. They usually only exist as oxide in the nature. e.g. Al2O3

Group IV elements are unreactive as it has a giant covalent structure(C, Si, Ge) and each atoms will form four strong covalent bonds to four other atom, making it very stable. Elements below Sn are metals, but they are difficult to lose electrons(half filled outermost electrons shell), result in low reactivity

Group V elements are more reactive than group IV elements because of a increasing nuclear charge and decreasing atomic radius. Bi and below elements has high reactivity as the same reason of metals in group IV.

Group VI elements are even more reactive than group V elements as the same reason of group V elements being more reactive than group IV's.

They are also reactive.
Only Group 0 elements are unreative.
而佢地reactivity ge 程度係由periodic table ge左至右而定
即係話:
Group 1喺periodic table係最左邊 ,所以最reactive
Group 2 係喺左邊計上去ge第2個,所以 2nd reactive
Group 0 係最右,所以最unreactive