The answer is A, biogeochemical cycles.
Answer:
Ca(Calcium)
20 electrons
2 valence electrons
4
Explanation:
Moles=2.04×10^(-6)
No. Of moles=no. Of particles/ Avogadro's no
(Where no. Of particles may be atoms molecules or compounds)
Moles=1.23×10^18/6.022×10^23
Moles=0.204×10^(-5)