Elements like barium located toward thr bottom of a group have a lower attraction for their valence electrons because they have a

Barium has a lower attraction for their valence electrons because there are a large number of electrons between the valence electrons and nucleus. And these electron cause great repulsion.

Explanation:

Barium is an alkaline earth metal and it's atomic number is 56 with electronic configuration [tex]1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^{2}4p^{6}4d^{10}5s^{2}5p^{6}6s^{2}.

This results in more number of shells in a barium atom. Hence, valence shell moves far away from the nucleus due to this there is very less attraction between the valence electrons and nucleus of Ba atom.

Thus, we can conclude that elements like barium located toward the bottom of a group have a lower attraction for their valence electrons because they have greater atomic mass.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

affects the water bodies: excessive use of fertilizers causes eutrophication. the fertilizers which are used on plants affect the quality of land on which it is used, further causing erosion of soil. the fertilizers used on plants contain harmful chemical fumes which affect the environment.