Nutrients circulate endlessly throughout many of the spheres in complex cycles called cylces.
a. biogeochemical
b. eutrophication
c. phosynthetic-respitory
d. hypoxic

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

it takes on an electronical energy