Density= Mass/Volume I am positive I just had an assignment on this
It might be c, because he came up with the plum pudding model. or it might be that atoms of the same element are identical, but that's not true cuz ions are different and isotopes are different.
It is B that one has the most mass
B. Increasing the effective nuclear charge on an ion results in energy levels that are closer together.
hope it helps
