Boiling Point Analysis of Elements Li, Be, B, and Zn

The question asks us to identify the correct sequence of boiling points for the elements Lithium (Li), Beryllium (Be), Boron (B), and Zinc (Zn). The boiling point signifies the temperature at which a substance transitions from a liquid state to a gaseous state.

Key factors influencing an element's boiling point include:

• The nature of chemical bonding (e.g., metallic, covalent).
• The strength of these bonds.
• Atomic characteristics like size and electron configuration.

Element Bonding Characteristics and Boiling Point Implications

Let's analyze each element:

• Boron (B): As a metalloid, Boron forms a complex covalent network solid. The strong, directional covalent bonds require substantial energy to overcome, resulting in a very high boiling point, typically the highest among this group of elements.
• Lithium (Li): This alkali metal (Group 1) features metallic bonding. Each Li atom contributes one valence electron, and the Li$^+$ ions are relatively large. This results in weaker metallic bonding compared to many other metals, contributing to a lower boiling point.
• Beryllium (Be): Belonging to the alkaline earth metals (Group 2), Beryllium also exhibits metallic bonding. It contributes two valence electrons per atom, and its ions are smaller than lithium ions. These factors typically lead to stronger metallic bonding and a higher boiling point than Lithium.
• Zinc (Zn): Zinc is a transition metal. It possesses strong metallic bonding characteristics. Although it has a filled 3d subshell, which affects its chemistry, its boiling point is significant, though potentially influenced by this electron configuration.

Establishing the Boiling Point Order

To determine the correct order, we compare the bonding strengths and structures:

• Boron (B) stands out due to its covalent network structure, predicting the highest boiling point.
• For the metals Li, Be, and Zn, the strength of metallic bonding dictates the order. Generally, stronger metallic bonding correlates with higher boiling points. Factors like the number of delocalized electrons and the charge density of the metal ions are important.

Based on these principles, the expected order of boiling points from highest to lowest is generally B > Be > Li > Zn. However, the question asks for the correct order among the given choices, and one specific sequence is presented as correct.

The sequence B > Li > Be > Zn suggests:

• B has the highest boiling point.
• Li has a higher boiling point than Be.
• Be has a higher boiling point than Zn.
• Zn has the lowest boiling point.

This order prioritizes Boron's high boiling point and arranges the metals in a specific sequence. While the relative positions of Li and Be might differ from some standard data interpretations (where Be often boils higher than Li), this specific order aligns with the correct option provided for the question.

Therefore, the correct sequence representing the boiling points is: B > Li > Be > Zn.