How is it possible that as atoms get more massive they become smaller is size?
Vocabulary atomic nucleus atomic radius effective nuclear charge electron period valence electron valence shell Suppose you wanted to determine the size of a swarm of bees. Counting the bees won’t do: you want the size or volume of the swarm, not the number of bees or the mass. One approach is to draw an imaginary line around the swarm. A few bees will cross the line, now and then, but the size of the boundary should give you some idea of the size of the swarm. Like swarms of bees, atoms don’t really have well-defined surfaces. They’re soft, diffuse objects. Electrons can be found at any distance from the nucleus. After a certain distance from the nucleus the swarm of electrons gradually thins, but never entirely disappears. However, an imaginary boundary surface can be drawn around the atom that contains (say) 99% of the electron density, and we can then refer to the size of the boundary surface as the size of the atom. What effect does an additional electron have on atomic size? Drop
