Question

The non-metal character of boron is indicated by (1) reaction with metals forming borides (2) libcration of hydrogen with alkalis (3) basic nature of its oxide (4) reaction with metals forming alloys

Short answer

The correct answer is (2) liberation of hydrogen with alkalis.

Step-by-step solution

Understand the Character of Non-metals

Non-metals typically form acidic oxides, do not react to form alloys, and often form covalent compounds.

Eliminate Incorrect Options

From the given options, reaction with metals forming borides (1) and forming alloys (4) indicates metallic behavior. Therefore, they can be eliminated.

Analyze the Remaining Options

Option (3) states that boron oxide is basic; however, non-metals usually have acidic oxides, making this option incorrect.

Identify the Correct Option

Option (2) states the liberation of hydrogen with alkalis, which is a characteristic reaction of non-metals with alkalis indicating the non-metallic nature of boron.

Key concepts

non-metals

Non-metals are a diverse group of elements found on the right side of the periodic table. Unlike metals, which are shiny, malleable, and conductive, non-metals tend to have opposite characteristics. They are usually dull, brittle, and poor conductors of heat and electricity. Most non-metals form acidic oxides, meaning their oxides react with water to form acids. Non-metals also tend to form covalent compounds, where they share electrons with other atoms. Examples of non-metals include oxygen (O), nitrogen (N), and sulfur (S). The behavior of non-metals can be complex, influencing how they react with other substances.

borides

Borides are compounds formed when boron reacts with metals. These compounds exhibit a combination of both metallic and non-metallic characteristics. Borides often involve a metal and boron sharing electrons in a way that creates a strong, rigid structure. For instance, titanium boride (TiB2) is known for its high hardness and resistance to corrosion. When boron forms borides with metals, it indicates some metallic behavior, which is different from the typical characteristics of non-metals. This dual nature is part of what makes boron's chemistry fascinating and important to understand.

acidic oxides

Acidic oxides are oxides that, when dissolved in water, form acidic solutions. They are typically formed from non-metals. For instance, when sulfur dioxide (SO2) dissolves in water, it forms sulfurous acid (H2SO3). This characteristic helps distinguish non-metals from metals because metallic oxides usually form basic solutions. Boron, as a non-metal, generally forms acidic oxides like boron trioxide (B2O3), which dissolves in water to form boric acid (H3BO3). This property is important to understand because it influences how non-metals behave in various chemical reactions.

reaction with alkalis

Non-metals often react with alkalis to liberate hydrogen gas. This reaction helps to identify the non-metallic nature of an element. When a non-metal like aluminum reacts with a strong alkali such as sodium hydroxide (NaOH), hydrogen gas is released. For boron, its reaction with alkalis like NaOH also releases hydrogen, confirming its non-metallic character. This sort of reaction is different from how metals might react, further distinguishing the behaviors of non-metals. Understanding these reactions can clarify why certain classification decisions are made in chemistry.