1. Sodium (Na) reacts with sulfur (S) to form a compound in the ratio of two sodium atoms to one sulfur atom. Element X also reacts with sodium in the ratio of two sodium atoms to one element X atom. Which is most likely the identity of element X? A. argon (Ar)
B. chlorine (Cl)
C. oxygen (O)
D. phosphorus (P)

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.