Question

Boron differs from the other members of III A group because it (1) has much lesser radius. (2) is a non metal. (3) is covalent in its compounds. (4) has a maximum covalency of 6 .

Short answer

The correct options are (1), (2), and (3). Option (4) is incorrect.

Step-by-step solution

Identify Boron's Group

Boron belongs to Group III A (also known as Group 13) of the periodic table.

Analyze Option 1

Determine if Boron has a much lesser radius compared to other elements in Group III A. The atomic and ionic radii generally increase down the group.

Evaluate Option 2

Check whether Boron is the only non-metal in Group III A. Boron is indeed a non-metal while other elements in this group are typically metals or metalloids.

Evaluate Option 3

Determine if Boron forms covalent compounds. Boron commonly forms covalent bonds due to its small size and high ionization energy.

Evaluate Option 4

Check if Boron can have a maximum covalency of 6. Boron typically exhibits a maximum covalency of 4 due to having only three valence electrons.

Conclusion

Based on the analysis, options 1, 2, and 3 are valid attributes of Boron, but Option 4 is incorrect since Boron cannot exhibit a covalency of 6.

Key concepts

atomic radius of Boron

The atomic radius of an element is the distance from the center of the nucleus to the outermost shell of electrons.
In the periodic table, boron is located in Group III A or Group 13. Among these group elements, boron has the smallest atomic radius.
This is because, as you move down the group, additional electron shells are added, increasing the size of the atoms.
Boron's smaller atomic radius has key implications:

• It provides a higher effective nuclear charge, meaning the nucleus pulls the electrons closer and more tightly.
• Smaller atomic radius makes atoms more electronegative and prone to forming covalent bonds.

Thus, boron's significantly smaller atomic radius is one of the critical differences between it and the other Group III A members.

covalent bonds

Boron often forms covalent bonds in its compounds.
A covalent bond occurs when atoms share electrons to fill their outermost electron shells. For boron:

• It has an electron configuration of 1s²2s²2p¹ and requires three more electrons to complete its octet.
• Boron typically shares these electrons with other atoms rather than donating or accepting them, hence forming covalent bonds.

Examples include boron trifluoride (BF₃) and borane (BH₃).
Covalent bonding is essential because:

• It impacts the chemical properties and reactivity of boron's compounds.
• It explains why boron compounds tend to have distinct molecular geometries.

Boron's covalent bonding tendency sets it apart from the other elements in Group III A, which frequently form ionic or metallic bonds.

non-metallic nature of Boron

Boron is unique in Group III A (Group 13) as it is the only non-metal. This characteristic influences its properties and reactions.
Unlike the metallic elements in the same group, boron:

• Does not have free electrons, making it a poor conductor of electricity.
• Has higher ionization energies, making it harder to lose electrons and more likely to form covalent bonds.
• Possesses a lower melting point compared to its metallic counterparts.

These properties make boron:

• Highly useful in producing heat-resistant materials like borosilicate glass.
• Critical in creating strong, lightweight materials for aerospace and high-strength fibers.

Understanding boron's non-metallic nature helps explain its divergence from the typical behaviors of its group.

group trends in periodic table

Studying trends in the periodic table helps to predict the properties of elements.
In Group III A (Group 13), certain patterns are evident:

• Atomic and ionic radii increase as you move down the group.
• Ionization energy decreases down the group because the outer electrons are further from the nucleus and thus easier to remove.
• Electronegativity generally decreases from boron to thallium.

Boron, at the top, sets several unique precedents for the group:

• It has the highest ionization energy and electronegativity in its group.
• The smallest size contributes to its non-metallic and covalent bonding nature, contrasting with the metallic properties of elements like aluminum and gallium.

These group trends are fundamental to understanding periodic behavior and predicting how elements within the same group might react or bond.