Question

The chemical reactivity of the elements of group I increases downwards while that of the element of group 17 decreases downwards. Explain​

Answer 1

The group 17 elements include fluorine(F), chlorine(Cl), bromine(Br), iodine(I) and astatine(At) from the top to the bottom. They are called “halogens” because they give salts when they react with metals. So, now you know what halogens are.

Answer 2

Group 1 elements are metals and they lose electrons easily on moving downwards whereas Group 17 elements are non metals and they gain electrons easily on moving upwards.

Explanation:

Chemical reactivity is defined as the tendency of an element to lose or gain electrons.

Non-metals are the elements which gains electrons and hence, their chemical reactivity will be the tendency to gain electrons.  Metals are the elements which lose electrons and hence, their chemical reactivity will be the tendency to lose electrons.

The chemical reactivity increases in Group 1 as we move from top to bottom in a group because the valence shell gets farther from the nucleus as we move from top to bottom. Thus, the removal of electron from the valence shell becomes easier due to lesser attraction between nucleus and valence electron.  Thus, the chemical reactivity of metals increases.

The chemical reactivity decreases in group 17 as we move from top to bottom in a group. As, the electrons get added up in the new shell, the electron in the outermost orbital gets far away from the nucleus. And hence, the electron will be difficult to gain. Thus, the chemical reactivity of non-metals decreases.

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