PH of a solution containing 0.81 M HA and 0.35M A-? Ka HA= 5.45x10^-8​

If a solution had a ph of 7 what is the solution

Select all of the statements which are true. electrons are located in shells or orbits around the atom. electrons orbit slowly around the atom. electrons travel in one flat path around the nucleus of an atom. the valence of an atom is determined by the number of electrons in the atom's outermost shell.

Which is true according to the law of conservation of energy