What is the Lewis dot structure for SiS2

An alloy contains 66 g of pure zinc. what is the percentage of zinc in the alloy? express your answer to two significant figures and include the appropriate units.

As changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit

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.