Given that oxygen see saying and i was just going to 18 both have an atomic number of 8 how many electrons protons and neutrons does these oxygen atoms contain

Number of protons = atomic number, assumed number of electrons = number of protons (all elements in the periodic table are assumed to have a neutral charge, in which case protons and electrons are equal in number. If this is not the case they will be ions of a certain element and wil have a + or - sign next to them.), number of neutrons= atomic wt - atomic number.  Oxygen has an atomic number of 8 and an atomic wt of 16 so protons = 8, electrons = 8 and neutrons = 16-8, or 8

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water