In comparison to an atom of f-19 in the ground state, an atom of c-12 in the ground state has(1) three fewer neutrons
(2) three fewer valence electrons
(3) three more neutrons
(4) three more valence electrons

Which theory was contradicted by experiments with the photoelectric effect? light spreads out after it passes through a small opening. as soon as light strikes metal, electrons will be ejected. visible light, regardless of color, will cause the ejection of electrons when striking metal. the kinetic energy of ejected electrons depends on the frequency of light that strikes the metal.