Which of the following statements about the bonding atomic radii in Figure 7.7 is incorrect? (i) For a given period, the radii of the representative elements generally decrease from left to right across a period. (ii) The radii of the representative elements for the n = 3 period are all larger than those of the corresponding elements in the n = 2 period. (iii) For most of the representative elements, the change in radius from the n = 2 to the n = 3 period is greater than the change in radius from n = 3 to n = 4. (iv) The radii of the transition elements generally increase moving from left to right within a period. (v) The large radii of the Group 1 elements are due to their relatively small effective nuclear charges.

Key Concepts

Atomic Radius Trends

The atomic radius refers to the size of an atom, typically measured from the nucleus to the outermost electron shell. In general, atomic radii decrease across a period from left to right due to increasing nuclear charge, which pulls electrons closer to the nucleus. Conversely, atomic radii increase down a group as additional electron shells are added, increasing the distance between the nucleus and the outermost electrons.

Effective Nuclear Charge (Z_eff)

Effective nuclear charge is the net positive charge experienced by an electron in a multi-electron atom. It accounts for the shielding effect of inner-shell electrons that reduce the full nuclear charge felt by outer-shell electrons. A higher effective nuclear charge leads to a stronger attraction between the nucleus and the outer electrons, resulting in smaller atomic radii, particularly across a period.

Comparative Periodic Trends

Comparative periodic trends involve analyzing how properties such as atomic radius, ionization energy, and electronegativity change across periods and down groups in the periodic table. For instance, while atomic radii generally decrease across a period, they can exhibit different behaviors in transition metals and lanthanides due to electron-electron interactions and subshell filling, which can complicate straightforward comparisons.