Who was the first to propose the idea of atoms

Find the mass in grams of 1.37x1020 particles of h3po4

In the millikan oil drop experiment they determined that every drop had a charge which was a while number multiple of -1.60x10^-19. if a drop has a total charge of -9.60x10^-19 then how many excess electrons are contained within the drop?

Which liquid (h2o, h2o + soap, or h2o + salt) has the strongest cohesion and adhesion? (need now plz)