Question

Stability of \(\mathrm{Ge}^{2+}, \mathrm{Sn}^{2+}\) and \(\mathrm{Pb}^{2+}\) is in order (a) \(\mathrm{Ge}^{2+}>\mathrm{Sn}^{2+}>\mathrm{Pb}^{2+}\) (b) \(\mathrm{Sn}^{2+}>\mathrm{Ge}^{2+}>\mathrm{Pb}^{2+}\) (c) \(\mathrm{Pb}^{2+}>\mathrm{Sn}^{2+}>\mathrm{Ge}^{2+}\) (d) \(\mathrm{Sn}^{2+}>\mathrm{Pb}^{2+}>\mathrm{Ge}^{2+}\)

Short answer

(c) \( \mathrm{Pb}^{2+} > \mathrm{Sn}^{2+} > \mathrm{Ge}^{2+} \)

Step-by-step solution

Introduction to stability

The stability of oxidation states in elements can vary due to the inert pair effect—a common trend observed in the p-block elements. This effect is more pronounced as we move down the group in the periodic table.

Understanding the Inert Pair Effect

The inert pair effect refers to the reluctance of the s-electrons to participate in bonding as we move down a group. This arises because the electrons in the s-orbital are more tightly bound to the nucleus and become less inclined to participate in chemical bonding.

Evaluating Ge, Sn, and Pb

As we move from Ge to Pb, the inert pair effect becomes more significant. This means the stability of the +2 oxidation state increases from Ge to Pb due to increased reluctance of the s-electrons to get involved in bonding.

Conclusion from trend analysis

Based on the inert pair effect, lead (Pb) in the +2 oxidation state is more stable than tin (Sn) and germanium (Ge). Thus, the order of stability for the +2 oxidation state is Pb^{2+} > Sn^{2+} > Ge^{2+}.

Key concepts

p-block elements

P-block elements are found on the right side of the periodic table, consisting of groups 13 to 18. These elements have their outermost electrons in the p orbital, making them highly diverse in their chemical properties. P-block elements include a variety of metals, metalloids, and nonmetals, which is why their properties can vary widely.

One key feature of p-block elements is the variety of oxidation states they can exhibit. These elements often have multiple oxidation states due to the different ways in which they can share or exchange electrons. This versatility is largely due to the presence of both s and p orbitals that can participate in bonding.

The inert pair effect is particularly relevant for heavier p-block elements, which is why understanding these elements requires an appreciation for how their electrons behave as you move down the group in the periodic table. This effect can significantly influence the chemical behavior and the stability of certain oxidation states of these elements.

oxidation states

Oxidation states, or oxidation numbers, refer to the charge that an atom would have if all bonds to atoms of different elements were completely ionic. Oxidation states help to determine the electron configuration of an element, which is crucial for predicting its chemical behavior.

In p-block elements, the oxidation states can vary widely even within a single group. Taking the example of Group 14 elements like Ge, Sn, and Pb, we observe both +2 and +4 oxidation states.

The stability of these oxidation states is influenced by the inert pair effect. As atoms become heavier (from Ge to Pb), their inner s orbitals (and especially the electrons in these orbitals) become "inert" or less willing to participate in bonding. This causes a shift in stability, favoring the lower oxidation state (such as +2) over the higher one (+4) as we move downward in the group.

stability of ions

Ions are atoms or molecules that have gained or lost electrons, resulting in a net charge. The stability of an ion is a critical factor in predicting the behavior and reactivity of elements. For p-block elements, particularly Ge, Sn, and Pb, the stability of ions is heavily influenced by the inert pair effect.

This effect makes the +2 oxidation state more stable for lead (Pb), especially when compared to tin (Sn) and germanium (Ge). Here's why: as we move down from Ge to Pb, the 6s electrons in Pb become more resistant to bonding due to a combination of poor shielding, relativistic effects, and increased atomic size.

In practical terms, this means that lead prefers to exist as Pb^{2+} rather than Pb^{4+}, making it more stable in the +2 state. This trend ultimately explains why the stability of the +2 oxidation state increases going from Ge to Sn to Pb.