Which of the following statements correctly describes energy levels? answer review
a. in its outermost energy level, oxygen has 4 valence electrons.
b. the second energy level holds a maximum of eight electrons.
c. electrons can never move to a higher or lower energy level.
d. the greater the energy of the level, the farther away it is from the nucleus.
i think its b or c. in my opinion they're both correct, i may be wrong. can someone clarify?

Using a value of ksp = 1.8 x 10-2 for the reaction pbcl2 pb+2(aq) + 2cl -(aq). if the value of ksp was determined to be only 1.2 x 10-2: too much solid has dissolved. additional precipitate is forming. the solution is unsaturated. the ions are now combining to reduce their concentrations.

This classification of drug typically changes the brain's chemistry and reduces its ability to create its own endorphins.

Lab reagent, hypothesis test.a reference solution used as a lab reagent is purported to have a concentration of 5 mg/dl. six samples are taken from this solution and the following concentrations are recorded: (5.32, 4.88, 5.10, 4.73, 5.15, 4.75) mg/dl.these six measurements are assumed to be an srs of all possible measurements from solution.they are also assumed to have a standard deviation of 0.2, a normal distributin, and a mean concentration equal to the true concentration of the solution.carry out a significance test to determine whether these six measurements provide reliable evidence that the true concentration of the solution is actually not 5 mg/dl.