Kathleen is testing a mixture containing a certain substance. She takes a sample from the top and the bottom. The sample from the bottom has more of the substance than the sample from the top. What is this mixture? a solution
heterogeneous
homogenous

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

it means there are 3 atoms of oxygen

< > according to newton's third law of motion, forces always act in equal but opposite pairs. another way of saying this is for every action, there is an equal but opposite reaction.< >