I just need a full answer here not only so I can answer the question, but also so that I can learn. Locate the main groups of elements in each column on the periodic table, and identify the number of valence electrons there are in each element in a particular group. Infer why some elements are more reactive than others due to their number of valence electrons.

Number of valence electrons determine how fast or easy for an atom to gain stability. Either by gaining electrons or by losing electrons.

Group one and seven elements react fast because they only have one electron to gain or lose.

Explanation:

Number of valence electrons tell us the number of electrons an atom will gain or lose in order to attain stability in electron configuration.

All the elements in a particular group will have the same number of valence electrons as follows:

Group one - 1 valence electron

Group two - 2 valence electrons

Group three - 3 valence electrons

Group four - 4 valence electrons

Group five - 3 valence electrons

Group six - 2 valence electrons

Group seven - 1 valence electron

Group eight - 0 valence electron

Some elements are more reactive than the others because of the electron affinity, oxidation state and electronegativity of the atoms

For instance, elements in group 7 are more reactive than others because of their oxidation state and they have very high electronegativity.

Also, group one elements are more reactive because they only have one electron to loose.