Atomic Radii

Atomic Radii

Moving down Group 18, from helium to radon, atomic radius increases steadily — visible directly in Table 7.12, where the radius grows from 120 pm for He to 220 pm for Xe. As with any group, this happens because each successive noble gas has one more principal shell of electrons than the one above it, and the added shells push the outer electron cloud progressively farther from the nucleus, outweighing the increase in nuclear charge. This same growth in size is the underlying reason the group' …