Problem 54 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following statements is not correct for nitrogen? (a) its molecular size is small (b) it is a typical non-metal (c) d orbitals are available for bonding (d) its electronegativity is very high

Step-by-Step Solution

Answer

Option (c) is incorrect because nitrogen lacks d orbitals for bonding.

Step 1: Analyzing Option (a)

The statement 'its molecular size is small' refers to the diatomic molecule of nitrogen, which is indeed small because it consists of two nitrogen atoms. Therefore, this statement is correct.

Step 2: Analyzing Option (b)

The statement 'it is a typical non-metal' is correct because nitrogen, as an element in group 15 of the periodic table, displays properties characteristic of non-metals. It is a gas at room temperature and forms negative ions in reactions.

Step 3: Analyzing Option (c)

The statement 'd orbitals are available for bonding' is incorrect because nitrogen has no available d orbitals for bonding. Its electronic configuration is 1s² 2s² 2p³, and it does not have empty d orbitals beyond the second period (n=2). This makes this statement incorrect.

Step 4: Analyzing Option (d)

The statement 'its electronegativity is very high' is correct as nitrogen is one of the most electronegative elements, with an electronegativity value of 3.04 on the Pauling scale, second only to fluorine and oxygen.

Key Concepts

Molecular Size

Nitrogen, being a diatomic molecule, is quite small in size. The molecule is written as \(N_2\) and consists of two nitrogen atoms. Due to the strong triple bond between the nitrogen atoms, \(N \equiv N\), the overall molecular size is compact. The triple bond is among the strongest in nature, making \(N_2\) a very stable molecule. As a result, the molecule also has a quite short bond length, contributing to its small molecular size. This feature is significant in many aspects of nitrogen's behavior, such as its role as an inert gas and its low reactivity under normal conditions.

Some key points about the molecular size of nitrogen include:

• The strong triple bond leads to a very short bond length.
• Its compact size results in low reactivity with other elements under standard conditions.
• The small size and low reactivity make nitrogen a major component of Earth's atmosphere.

Non-Metal Properties

Nitrogen is a typical non-metal and showcases several properties common to non-metals. These properties are primarily due to its position in Group 15 of the periodic table. Non-metals, including nitrogen, typically exist in gaseous states at room temperature. Nitrogen gas is colorless, odorless, and tasteless, characteristics often found in non-metals.

Here are some defining non-metal properties of nitrogen:

• It forms negative ions by gaining electrons in reactions.
• It has a high ionization energy, which distinguishes it from metals.
• The ability to form covalent bonds is a key feature, allowing it to form a variety of compounds like ammonia \(NH_3\), nitric acid \(HNO_3\), and others.
• Nitrogen's inability to conduct electricity is typical of non-metals, as it involves covalent bonding with no free electrons.

Understanding these properties helps in clearly identifying nitrogen as a non-metal, especially in chemical reactions.

Electron Configuration

The electron configuration of an element describes how electrons are distributed in its atomic orbitals. For nitrogen, the electron configuration is \([1s^2 \ 2s^2 \ 2p^3]\). This configuration highlights two main things about nitrogen:

• It has five electrons in its outer shell.
• Due to the \(2p^3\) configuration, nitrogen is three electrons short of a full octet, making it eager to form bonds to achieve a stable electron arrangement.

One critical aspect to notice is that nitrogen does not have d orbitals available for bonding, as it is located in the second period (n=2) where only s and p orbitals are implicated. This limited availability makes nitrogen's chemistry largely confined to s and p block interactions. This aspect is particularly important when considering its behavior in forming covalent and Ionic bonds.

Electronegativity

Electronegativity is the tendency of an atom to attract electrons towards itself when bonded to another atom. Nitrogen is known for its high electronegativity, which is measured to be 3.04 on the Pauling scale. This makes it one of the most electronegative elements, surpassed only by fluorine and oxygen.

Because of its high electronegativity:

• Nitrogen frequently forms polar covalent bonds, such as in \(NH_3\), where it draws electrons toward itself and creates a partial negative charge.
• Its high electronegativity is the reason for its common characteristic of forming hydrogen bonds, particularly evident in weak interactions in biological systems like DNA and proteins.
• This characteristic of attracting shared electrons makes nitrogen very significant in the chemistry of life, contributing to the structural and functional compounds such as amino acids and nucleotides.

High electronegativity is a hallmark of how nitrogen interacts in a multitude of chemical environments, allowing it to play crucial roles in various biological and chemical processes.