Question

Which of the following is not the point of difference between Be and other alkaline earth metals? (a) It has a tendency to form covalent bonds. (b) It dissolves in alkalies with evolution of hydrogen. (c) Its oxides and hydroxides are amphoteric. (d) Its carbide gives acetylene on hydrolysis.

Short answer

Option (b) is not the point of difference between Be and other alkaline earth metals.

Step-by-step solution

Understand the properties of Beryllium

Recognize that Beryllium (Be), unlike other alkaline earth metals, prefers to form covalent bonds because of its small size and high ionization energy.

Examine other alkaline earth metal properties

Other alkaline earth metals (such as Mg, Ca, Sr, Ba) typically form ionic bonds, do not dissolve in alkalies to evolve hydrogen, and their oxides and hydroxides are not amphoteric but rather basic.

Identify the incorrect statement

Compare the given options with the known properties of Beryllium and other alkaline earth metals to identify the statement that is not a point of difference between them.

Analyze each option

Option (a) is true, as Beryllium forms covalent bonds. Option (b) is false for Beryllium but true for other alkaline earth metals, making this the characteristic not unique to Beryllium. Option (c) is true, as Beryllium oxides and hydroxides are amphoteric. Option (d) is true, Beryllium carbide does give acetylene upon hydrolysis like other alkaline earth metals.

Key concepts

Beryllium Chemical Properties

Beryllium, symbolized as Be, is quite unique among the group of alkaline earth metals. It is known for its small atomic size and high ionization energy. These properties influence Beryllium to form covalent bonds rather than ionic bonds, which is unusual for metals in its group. Covalent bonding occurs because Beryllium's small size allows orbitals to overlap sufficiently, facilitating the sharing of electrons between atoms.

Another notable property of Beryllium is its reaction to hydrolysis. While many metals react with water to release hydrogen gas, Beryllium carbide (Be2C) on hydrolysis produces acetylene (C2H2) instead. This reaction showcases its ability to form complex chemical compounds. In terms of reactivity, Beryllium does not typically react with water or dilute acids, which again sets it apart from its group members. Its high melting point and excellent thermal conductivity are exploited in various industrial applications making it a material of interest in fields such as aerospace and nuclear technologies.

Covalent and Ionic Bonds

Covalent and ionic bonds are two of the primary types of chemical bonds between atoms. Covalent bonds involve the sharing of electron pairs between atoms, leading to the formation of molecules. This type of bonding is prevalent in organic compounds and often occurs between nonmetals. For instance, in Beryllium compounds, such as Beryllium chloride (BeCl2), the atoms share electrons, producing a covalent bond.

On the other hand, ionic bonds are formed when one atom donates electrons to another, resulting in a pair of oppositely charged ions. This type of bond is common in salts and is typically observed in compounds of the heavier alkaline earth metals like calcium, magnesium, strontium, and barium. In contrast, due to Beryllium's small size and high ionization energy, it prefers to form covalent bonds making its chemistry distinct from its counterparts in the same group.

Amphoteric Oxides and Hydroxides

The concept of amphoteric substances is fascinating as these compounds can behave as both acids and bases. Beryllium's oxides and hydroxides are examples of amphoteric compounds. For instance, beryllium oxide (BeO) and beryllium hydroxide (Be(OH)2) can react with acids and bases to form salts and water, showcasing their dual acidic and basic properties. This is in stark contrast to the oxides and hydroxides of other alkaline earth metals which, due to their higher metallic character, typically exhibit purely basic behavior.

Understanding the amphoteric nature of Beryllium compounds is essential for grasping their chemical reactivity and potential applications. For example, the ability to react with both acids and bases makes BeO useful as a refractory material in furnaces and kilns. Beryllium hydroxide's reaction with acids and bases also demonstrates its versatility in various chemical reactions. The amphoteric behavior is a result of Beryllium's position on the periodic table, bridging the nonmetals and the heavier alkaline earth metals.