What type of chlorophyll does the reaction center contain

Chlorophyll "a"

Explanation:

The reaction centers of the photosystem have chlorophyll "a" molecules. The chlorophyll "a" that functions as a reaction center for the photosystem II has absorption maxima at 680 nm and therefore, it is called P680. The reaction center of photosystem I also have chlorophyll "a" molecules that have the absorption peak at 700 nm. The chlorophyll "a" molecules serving as reaction centers transfer the photoexcited electrons to a primary acceptor during the light-dependent phase of photosynthesis.

they float because they are less dense than the water itself

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

rocks and weathering-matching