Question

STATEMENT-1 : Boron always forms covalent bond. because STATEMENT-2: The small size of \(\mathrm{B}^{3+}\) favours formation of covalent bond. (A) Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1 (B) Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1 (C) Statement- 1 is True, Statement-2 is False (D) Statement-1 is False, Statement-2 is True

Short answer

Statement-1 is True since boron, due to its small size, high ionization energy, and absence of d-orbitals, forms covalent bonds. Statement-2 is also True as the small size of boron leads to a high charge density, which results in polarization of bonds and increased covalent character. However, Statement-2 is not the correct explanation as the ionic form \(\mathrm{B}^{3+}\) is rarely seen and does not directly explain boron's covalent bonding tendency. Thus, option (B) is correct.

Step-by-step solution

Analyze Statement-1

Investigate the validity of the claim that Boron always forms covalent bonds. Look for evidence in chemical behavior and bonding tendencies of Boron.

Examine Statement-2

Evaluate the truthfulness of the statement that the small size of \(\mathrm{B}^{3+}\) favors the formation of covalent bonds, considering the principles of chemical bonding and ionic versus covalent character.

Assess the Relationship

Determine if Statement-2 provides a correct explanation for Statement-1 by connecting the concepts mentioned in Statement-2 with the behavior described in Statement-1.

Key concepts

Covalent Bond Formation

Understanding covalent bond formation is key to comprehending how atoms like boron connect with other elements. A covalent bond occurs when two atoms share one or more pairs of electrons. This happens due to the atoms' desire to achieve a full outer shell of electrons, which leads to greater stability—an idea known in chemistry as the octet rule.

Consider the simplest example, a hydrogen molecule (H2). Each hydrogen atom has one electron and wants two to complete its shell, so they link up, sharing their electrons to achieve that. Boron, with only three electrons in its outer shell, follows a similar logic, albeit slightly more complex given its position on the periodic table. To fulfill its octet, boron seeks to share electrons with other elements, leading primarily to the formation of covalent bonds rather than ionic ones.

When discussing boron, which is a small atom, its tendency to form covalent bonds is often attributed to its size relative to the charge on the ion it would form if it gained or lost electrons. Its ability to share electrons effectively is what makes it such an important player in organic and inorganic chemistry alike.

Boron Chemistry

Diving into boron chemistry, the element Boron (B) holds a fascinating place on the periodic table. It is a metalloid, meaning it has properties intermediate between metals and nonmetals. With an atomic number of 5, boron has five protons and typically five electrons. Three of these electrons are valence electrons, available for bonding.

Unique Behavior of Boron

Boron's small size and electron deficiency play a pivotal role in its chemical behavior, as it does not conform to the 'octet rule' as strictly as many other elements do. Instead of seeking to fill its outer shell with eight electrons (which is difficult due to having only three valence electrons), boron often forms compounds where it has six valence electrons. This deficiency leads boron compounds to have very interesting and useful reactivity, making them important in various applications from materials science to medicine.

Boron compounds typically exhibit covalent bonding. Due to its small size and high ionization energy, it's less energetically favorable for boron to form B3+ ions; thus, it leans towards forming covalent bonds. This inclination towards covalent bonding over ionic bonding is a distinctive feature of boron chemistry.

Ionic vs Covalent Bonds

When it comes to ionic vs covalent bonds, the primary difference is how the atoms involved hold onto their electrons. Ionic bonds form between metals and nonmetals when one atom donates its electron(s) to another, creating a bond due to the electrostatic attraction between oppositely charged ions. For instance, sodium (Na) can donate an electron to chlorine (Cl) to form table salt (NaCl), an ionic compound.

On the other hand, covalent bonds often form between nonmetal atoms when they share electrons to achieve full outer electron shells. These shared electrons create a stable balance of attraction: not fully transferred as in ionic bonds, but mutually attracted to the nuclei of both atoms involved.

Comparison with Boron

In contrast to metals that tend to lose electrons and form cations, boron does not easily form B3+ ions due to its high ionization energy and smaller size, which would result in a highly unstable ion. Instead, boron's properties steer it toward sharing electrons with other nonmetals, resulting in covalent bonds. Understanding this distinction helps explain why boron compounds exhibit the behaviors and properties they do, which are markedly different from ionic compounds.