A mixture of helium, nitrogen and oxygen has a total pressure of 741 mmHg. The partial pressure of helium is 158 mmHg, and the partial pressure of nitrogen is 180 mmHg. What is the partial pressure (in mmHg) of oxygen in the mixture?

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.