# Which is the bigger atom, argon or chlorine?

As a physical scientist, you should consult the data. See this site. The atomic radius of $A r$ is $71 \times {10}^{-} 12 \cdot m$; that of atomic chlorine is $79 \times {10}^{-} 12 \cdot m$. And this illustrates a general Periodic Trend: atomic size decreases across a Period from left to right as we face the Table; it INCREASES down a Group.