Question

Which of the following statements is false? (1) The most abundant metal in the Earth crust is aluminium. (2) Boron never form \(\mathrm{B}^{3-}\) ion. (3) Among III A elements, boron has the lowest melting point. (4) Owing to small size and more charge on \(\mathrm{M}^{3-}\) ion of III A group elements, their aqueous solutions are acidic, and their acidic nature increases from \(\mathrm{A} 1^{3-}\) to \(\mathrm{Tl}^{3+}\)

Short answer

Statement 3 is false; boron has a high melting point.

Step-by-step solution

- Understanding each statement

Carefully read and understand each of the given statements to identify if they are true or false based on your knowledge of chemistry.

- Evaluating Statement 1

Statement 1 claims that aluminium is the most abundant metal in the Earth's crust. Confirm this fact by reviewing geological data.

- Evaluating Statement 2

Statement 2 claims that boron never forms a \( \text{B}^{3-} \) ion. Verify this by noting that boron, due to its small size and high ionization energy, doesn't favor the formation of \( \text{B}^{3-} \) ions.

- Evaluating Statement 3

Statement 3 asserts that among Group III A elements, boron has the lowest melting point. Check the melting points of Group III A elements to verify this claim.

- Evaluating Statement 4

Statement 4 discusses the acidic nature of aqueous solutions containing \( \text{M}^{3+} \) ions in Group III A, increasing from \( \text{Al}^{3+} \) to \( \text{Tl}^{3+} \). Validate this by considering the nature of these ions and their influence on acidity.

- Conclusion

Based on the evaluations, compare the statements and determine which one is false.

Key concepts

group III A elements

Group III A elements, also known as the Boron group, include Boron (B), Aluminum (Al), Gallium (Ga), Indium (In), and Thallium (Tl). These elements have three electrons in their outermost shell, which defines their chemical properties.
They collectively exhibit a range of behaviors due to the differences in their atomic and physical properties:

• Boron (B): Boron is a metalloid with distinctive properties, such as high ionization energy and low reactivity.
• Aluminum (Al): Aluminum is a metal known for being lightweight and possessing good conductivity.
• Gallium (Ga): Gallium is a metal with an unusual melting point just above room temperature.
• Indium (In): Indium is a softer metal widely used in electronic devices.
• Thallium (Tl): Thallium is a highly toxic metal.

Each element’s melting point and other properties are significantly different due to variations in atomic size and structure. For example, boron has a very high melting point due to its strong covalent bonds, while indium and gallium have relatively lower melting points.

acidity of aqueous solutions

The acidity of aqueous solutions containing Group III A elements is largely influenced by the presence of \( M^{3+} \) ions. These ions have a high charge density due to their small ionic size, making them potent in attracting water molecules and strongly polarizing them. This leads to hydrolysis, yielding \( H^+ \) ions in the solution which increases its acidity.
Here are some key points on how this works:

• The water molecules surrounding \( M^{3+} \) ions become more polarized, weakening the \( O-H \) bond in the water molecule.
• This results in the release of \( H^+ \) ions into the solution, increasing its acidity.

The trend in acidity among Group III A elements’ ions is influenced by the charge and size of the ions:

• Lower ionic size and higher charge result in higher acidity.
• Therefore, acidity typically increases from \( Al^{3+} \) to \( Tl^{3+} \) as you move down the group due to the increasing size and constant charge.

abundance of metals

When discussing elements in terms of their abundance, it is important to note that certain metals are more prevalent due to geological and environmental factors. Aluminum (Al) is the most abundant metal in the Earth's crust, making up about 8.23% of it.
Some reasons why aluminum is so abundant include:

• It is highly reactive, which allows it to combine readily with other elements.
• Aluminum is often found in compounds such as bauxite and aluminum oxide.

Other metals like iron and calcium are also abundant but don’t surpass aluminum in terms of crustal content. Comparing with boron, which is much less abundant and typically found in specific minerals such as borates and borosilicates: Aluminum's high abundance fits well into industrial and economic contexts, making it highly valuable for manufacturing and construction.

boron chemistry

Boron chemistry is fascinating due to boron's unique position as a metalloid and its chemical properties. Boron does not form \( B^{3-} \) ions due to its high ionization energy and small size, making it unlikely to gain three electrons.
Here are key points about boron chemistry:

• Boron typically forms covalent bonds rather than ionic bonds.
• In compounds, it typically exhibits oxidation states of +3 or +1.
• Boron compounds, like borates and boranes, are used in a variety of applications including detergents, insecticides, and electronics.

In terms of physical properties, boron has:

• A high melting point due to its strong covalent bonds in its lattice structure.
• Unusual structures in its compounds, such as boranes having 3-center 2-electron bonds.

These diverse properties make boron a unique and versatile element in both industrial and chemical settings.