Consider the isoelectronic ions: K^+, S^2, C 1 and C a^2 t....

Consider the isoelectronic ions: $K^{+}, S^{2}, C 1$ and $C a^{2 t}$. The radii of these ionic species follow the order (a) $\mathrm{Ca}^{2 *}>\mathrm{K}+>\mathrm{Cl}>\mathrm{S}^{2-}$ (b) $\mathrm{Cl}>\mathrm{S}^{2-}>\mathrm{K}^{+}>\mathrm{Ca}^{2+}$ (c) $\mathrm{S}^{2-}>\mathrm{Cl}>\mathrm{K}^{*}>\mathrm{Ca}^{2+}$ (d) $\mathrm{K}^{+}>\mathrm{Ca}^{2+}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}$

Consider the isoelectronic ions: $K^{+}, S^{2}, C 1$ and $C a^{2 t}$. The radii of these ionic species follow the order
(a) $\mathrm{Ca}^{2 *}>\mathrm{K}+>\mathrm{Cl}>\mathrm{S}^{2-}$
(b) $\mathrm{Cl}>\mathrm{S}^{2-}>\mathrm{K}^{+}>\mathrm{Ca}^{2+}$
(c) $\mathrm{S}^{2-}>\mathrm{Cl}>\mathrm{K}^{*}>\mathrm{Ca}^{2+}$
(d) $\mathrm{K}^{+}>\mathrm{Ca}^{2+}>\mathrm{S}^{2-}>\mathrm{Cl}^{-}$

Key Concepts

Isoelectronic Species

Isoelectronic species are atoms or ions that have the same number of electrons. Despite having identical electron counts, differences in nuclear charge lead to variations in their physical properties, particularly their size. This concept is crucial for comparing ions like K?, S²?, Cl?, and Ca²?, where the distribution of electrons is the same, but the number of protons in the nucleus differs.

Effective Nuclear Charge

Effective nuclear charge refers to the net positive charge experienced by the electrons in an atom or ion after accounting for the shielding effect of inner electrons. In isoelectronic species, a higher effective nuclear charge pulls electrons closer to the nucleus, resulting in a smaller ionic radius. This principle explains why ions with more protons in the nucleus are generally smaller than those with fewer protons.

Ionic Radii

Ionic radii represent the size of an ion, which is influenced by the balance between the nuclear charge and electron-electron repulsions. When comparing isoelectronic ions, the ionic radius is primarily determined by the effective nuclear charge. As the nuclear charge increases within an isoelectronic series, the ions contract, making the ion with the highest nuclear charge the smallest.

Periodic Trends

Periodic trends, such as the variation in atomic and ionic sizes across the periodic table, are driven by changes in nuclear charge and electron shielding. For isoelectronic ions, understanding these trends helps predict relative sizes, where an increase in nuclear charge corresponds with a decrease in radius. This concept helps in comparing the sizes of ions even when they have the same number of electrons.

Transcript

Please give Ace some feedback