Question

Explain the following variations in atomic or ionic radii:

(a) i - 7 i 7 i
(b) ca 2 7 mg2 7 be 2
(c) fe 7 fe 2 7 fe 3

Options:
a) (a) Shows an increasing ionic radius; (b) represents elements in the same group; (c) demonstrates a decrease in ionic radii.
b) (a) Indicates anionic radii trend; (b) displays elements of different groups; (c) illustrates the variation in atomic radii.
c) (a) Represents an irregular pattern in atomic radii; (b) signifies elements in the same period; (c) demonstrates variations in ionic radii.
d) (a) Indicates a constant ionic radius; (b) represents elements in different periods; (c) displays a consistent trend in atomic radii.

Answer 1

The variation in atomic or ionic radii is explained by electronic configurations and effective nuclear charge: (a) shows increasing ionic radii for anions, (b) represents increasing radii down a group, and (c) shows decreasing ionic radii with increasing charge.

Step-by-step explanation:

The question pertains to the variations in atomic or ionic radii. Option (a) indicates a trend in ionic radii where anions typically have larger radii than their parent atoms. This is because anions have gained electrons but the nuclear charge remains constant, leading to increased electron-electron repulsions and a larger radius. Conversely, cations are smaller than their parent atoms due to losing electrons, which increases the effective nuclear charge on the remaining electrons, pulling them closer to the nucleus. Option (b) relates to the trend that elements within the same group of the periodic table (such as the alkaline earth metals like Ca, Mg, and Be) have increasing ionic radii as we move down the group because the principal quantum number (n) increases. Option (c) explores the trend in the ionic radii of transition metals like Fe. As the ionic charge increases (Fe to Fe2+ to Fe3+), the ionic radius decreases due to the higher effective nuclear charge, which pulls the electrons closer to the nucleus and reduces the size of the ion.