Question

Discuss the pattern of variation in the oxidation states of (i) B to Tl and (ii) \(\mathrm{C}\) to \(\mathrm{Pb}\).

Short answer

The oxidation states in groups 13 (B to Tl) and 14 (C to Pb) show a trend toward lower states (+1, +2) in heavier elements due to the inert pair effect.

Step-by-step solution

Understanding Oxidation States

The oxidation state, or oxidation number, represents the degree of oxidation (loss of electrons) of an atom in a chemical compound. Oxidation states can help us understand the electron transfer in chemical reactions.

Analyzing B to Tl Oxidation States

Elements from boron (B) to thallium (Tl) belong to group 13 of the periodic table. The common oxidation states for these elements are +3 and +1. The +3 state is more stable for lighter elements like B and Al, while the +1 state becomes more stable as we move down the group towards Tl due to the inert pair effect, which makes the s-electrons less available for bonding.

Analyzing C to Pb Oxidation States

Elements from carbon (C) to lead (Pb) belong to group 14 of the periodic table. The common oxidation states for these elements are +4 and +2. The +4 state is more stable for lighter elements like C and Si, whereas the +2 state becomes more common for heavier elements like Sn and Pb, predominantly due to the inert pair effect, which causes the s-electrons to remain non-bonding in heavier elements.

Pattern Explanation for B to Tl

The transition from a more stable +3 oxidation state in boron and aluminum to a more stable +1 state in thallium can be attributed to the increasing impact of the inert pair effect as we move down the group. As a result, heavier elements like Tl are more likely to retain their s-electrons, leading to a prevalence of the lower oxidation state.

Pattern Explanation for C to Pb

In group 14, the transition from a prevalent +4 oxidation state in lighter elements like carbon and silicon to a prevalent +2 state in heavier elements like lead is again due to the inert pair effect. The s-electrons in heavier elements are less involved in bonding, resulting in a stable +2 state.

Conclusion of Trends

For both groups, the oxidation state patterns are influenced significantly by the inert pair effect, which stabilizes lower oxidation states in heavier elements due to the reluctance of s-electrons to participate in bonding.

Key concepts

Inert Pair Effect

The inert pair effect describes a phenomenon where the outermost s-electrons in heavier elements exhibit a reluctance to participate in chemical bonding. It primarily affects elements in group 13 and group 14 of the periodic table. This effect becomes more pronounced as we move down these groups.

• Elements like thallium and lead illustrate the inert pair effect prominently.
• The s-electrons remain paired and non-bonding, hence the term 'inert pair.'
• This effect leads to stabilization of lower oxidation states, like +1 and +2, in heavier elements.

Understanding this effect is crucial for predicting and explaining the chemical behavior of these elements. It highlights how heavier atoms can maintain their s-electrons, impacting their willingness to engage in chemical reactions.

Group 13 Elements

Group 13 elements include boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). These elements tend to form compounds primarily in the +3 oxidation state.

• Boron and aluminum readily form +3 oxidation states due to their ability to fully utilize all three p-electrons.
• As we proceed to heavier elements like thallium, a deviation occurs because of the inert pair effect.
• Thallium often exhibits a stable +1 oxidation state, preferring to retain its s-electrons.

This variation underscores how periodic trends influence the chemical properties of elements in this group. The shift in oxidation states from +3 to +1 is crucial for understanding the reactivity and bonding characteristics of these elements.

Group 14 Elements

Elements in group 14 include carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb). These elements show a shift from the common +4 oxidation state in lighter elements to +2 in heavier ones, primarily driven by the inert pair effect.

• Carbon and silicon are known to form stable compounds with a +4 oxidation state.
• For elements like lead, the +2 oxidation state becomes more prevalent due to the reluctance of s-electrons to participate in bonding.
• This change affects their usefulness and applications, such as lead being more common in its +2 state in industrial applications.

Recognizing this pattern aids in predicting the types of compounds these elements can form, affecting both their chemical and physical properties.

Electron Transfer

Electron transfer is a fundamental concept in chemistry, describing how electrons are moved from one atom to another. This process is intimately tied to the oxidation states of elements.

• When elements form compounds, electrons can be shared or transferred to achieve stable configurations.
• The oxidation state helps gauge the extent of electron transfer and can predict the type of bond—ionic or covalent.
• Electron transfer patterns, influenced by factors like the inert pair effect, dictate the chemical reactivity and stability of elements and their compounds.

By understanding how electrons are transferred or shared, students can better predict chemical reactions and the types of substances formed.

Periodic Trends

Periodic trends refer to predictable patterns seen in the properties of elements as one moves across or down the periodic table. These trends help scientists anticipate an element's chemical behavior and form the backbone of periodic law.

• Properties like electronegativity, ionization energy, and atomic radius exhibit clear trends across the periodic table.
• The inert pair effect is a consequence of such trends, particularly affecting oxidation states in groups 13 and 14.
• Understanding these trends supports the prediction of element reactivity and stability.

Periodic trends serve as a guide for chemists to understand element reactivities and how they interact to form compounds.