In 1912 a Danish physicist, Niels Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen. (This was a new approach to science because for the first time, rules were made to fit the observation even though they conflicted with present theories of the time.) Bohr said, “Here's some rules that seem impossible, but they describe the way atoms operate, so let's pretend they're correct and use them.” Two of Bohr's rules are as follows:
RULE 1: Electrons can orbit only at certain allowed distances from the nucleus.
RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. Also, an atom absorbs energy when an electron is boosted from a low-energy orbit to a high-energy orbit.
