Why doesn't a negative stain colorize the cells in the smear?

It is impossible for a negative stain to colorize the cells in the smear because the chromogen of the negative stain carries a negative charge and is repelled as a result of the negative charge present on the surface of the cell. In this light, the stain can only colorize the background, thus permitting visibility of the capsule and the cell.

Explanation:

they float because they are less dense than the water itself

something denser than water, like a rock, will sink to the bottom

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.