Among the elements of the main group, the general trend in the first ionization energy moving across a period is not followed between group 2 and group 13. Which best explains these exceptions? The ionization energy decreases because the full s orbital shields the electron entering the p orbital. The ionization energy increases because the full s orbital shields the electron entering the p orbital. The ionization energy decreases because the stability of the half-full p subshell is increased. The ionization energy increases because the stability of the half-full p subshell is increased.

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.