The fourth period contains 18 elements, beginning with potassium and ending with krypton. As a rule, period 4 elements fill their 4s shells first, then their 3d and 4p shells, in that order; however, there are exceptions, such as chromium.
Cr. I think
Answer:
Which scientist developed the first model of the atom that showed the structure of the inside of an atom
Ernest Rutherford
Science is constantly changing as new things are always being discovered, therefore "it is consistent and does not need to change with new discoveries" is false.
