Copper atoms might have more mass than aluminum atoms. Copper atoms might be smaller so more can fit in the same volume. Copper and aluminum atoms might be arranged differently so more copper atoms ...

That both of these rules should be violated by copper having the three isotopes 62, 64, 66, announced recently by Prof. Dempster, seemed therefore excessively improbable. Nature - The Mass ...

Copper atoms are larger than aluminum atoms. There are fewer copper atoms than aluminum atoms in the cubes. Copper atoms are much more massive than aluminum atoms. The extra mass makes copper more ...