Why do some metals loose their shine overtime but gold does not?

Theoretically, which metal should be the most reactive? hydrogen lithium francium fluorine

How could a student test the effect of removing heat from a gas that is stored in a sealed container? what must occur in order for matter to change states?

The bohr model of the atom explained why emission spectra are discrete. it could also be used to explain the photoelectric effect. which is a correct explanation of the photoelectric effect according to the model?