Why do posisons collect more in carnivores than in herbivores?

The simple answer is bioaccumulation resulting from biomagnification. Carnivores consume organisms at higher trophic levels, and thus "poisons," such as heavy metals accumulate in these organisms at levels greater than those found in plants. Moreover, such chemicals typically accumulate in the fatty tissues of carnivores, such as the nervous, lymphatic, endocrine, and reproductive systems.

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.