Joan and mike's teacher show them a picture of an atom and ask them to identify it using the periodic table. joan says the atom is carbon, but mike says it is lithium. who is right and why? mike is correct because the atomic number shows the number of protons in all atoms. there are 3 protons and the atomic number of lithium is 3. mike is right because the atomic mass of lithium is 6. there are 3 protons and 3 electrons in the atom. 3+3=6 joan is right because the atomic number of carbon is 6. there are 3 protons and 3 electrons in the atom. the atomic number shows the number of protons plus the number of electrons. 3+3=6 joan is correct because carbon is a neutral atom. there are the same number of protons and electrons in the atom pictured.

Well we can't see the picture that the teacher has, and we have to figure out what's in the picture from some clues in the answer choices.  The picture seems to show an atom with 3 protons and 3 neutrons in the nucleus, and 3 electrons whizzing around the nucleus.

If that's what's in the picture, then Mike is correct (first choice), because the atomic number shows the number of protons in all atoms. There are 3 protons and the atomic number of lithium is 3.

Second choice . . . False, because electrons are not involved in the atomic mass.

Third and fourth choices . . . both false; sadly, Joan is woefully unclear on the concepts.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.