Problem 119 - A Complete Resource Book in Chemistry for JEE Main

Question

9\. Which type of bond is not present in HNO \(_{2}\) molecule? (a) covalent (b) coordinate (c) ionic (d) ionic as well as coordinate

Step-by-Step Solution

Answer

Ionic bond is not present in HNO\(_2\).

Step 1: Understanding the molecule structure

Firstly, let's understand the structure of the HNO\(_{2}\) molecule. It consists of one hydrogen (H), one nitrogen (N), and two oxygen (O) atoms. The likely structure is H-O-N=O, where N is bonded to one O with a double bond and to another O through a single bond with an H attached to it.

Step 2: Analyze the bonds present

In the HNO\(_{2}\) molecule, examine the bonds: The N=O bond is covalent, formed by the sharing of electrons. The N-O-H part involves normal covalent bonding as well, with additional resonance characteristics. There is no electron pair donation typically described by coordinate bonding.

Step 3: Review bond types in the options

Covalent bonds are present due to shared electrons. A coordinate bond involves electron pair donation from one atom to another and isn't evident in HNO\(_{2}\). Ionic bonding involves complete electron transfer, which isn't present here since all atoms are nonmetals sharing electrons.

Step 4: Conclusion on bond types

From our analysis, the molecule includes covalent bonds only. Therefore, neither coordinate nor ionic bonds are present in HNO\(_{2}\).

Key Concepts

Covalent Bond

Atoms form covalent bonds by sharing electrons with one another. This type of bond usually occurs between nonmetal atoms. For instance, in the HNO89 molecule, the nitrogen and oxygen atoms share electrons to form a covalent bond. Similarly, the hydrogen atom also shares its electron with one of the oxygen atoms. Some important features of covalent bonds include:

• Electron sharing leads to the filling of outer electron shells, achieving stability akin to noble gases.
• Covalent bonds can be single, double, or triple, depending on the number of shared electron pairs.
• Such bonds give rise to molecules and molecular compounds.

Overall, covalent bonds are predominant in molecules like HNO89, where atoms achieve a stable electronic configuration by sharing electrons.

Coordinate Bond

A coordinate bond is a specific type of covalent bond. In a coordinate bond, the shared pair of electrons comes from one atom alone, often called the donor atom. This type of bonding is also known as a dative covalent bond. However, in the HNO89 molecule, we don't find coordinate bonding. Instead, all atoms engage in straightforward electron sharing without any single atom supplying both electrons in the bond.The absence of a coordinate bond in HNO89 can be attributed to:

• The lack of a typical donor-acceptor arrangement among the atoms.
• Each atom involved achieves stability through shared electron pairs, maintaining a standard covalent structure.

Understanding this type of bonding helps clarify why certain molecules possess unique properties and reactivities.

Ionic Bond

An ionic bond occurs when one atom donates an electron to another, resulting in a positive and negative ion that attract each other. This kind of bond usually happens between metal and nonmetal elements. It involves a full transfer of electrons, significantly differing from covalent bonds which include sharing.In the context of the HNO89 molecule:

• All participating atoms are nonmetals, which naturally tend toward covalent bonding via electron sharing.
• There is no occurrence of electron transfer significant enough to create ions.

Thus, ionic bonds are absent in HNO89, as the conditions necessary for electron transfer and ion formation are not met.

Molecular Structure

Molecular structure refers to the specific arrangement of atoms in a molecule. It influences how the molecule reacts and interacts with others. To determine the molecular structure of a molecule like HNO89, understanding the configuration and types of bonds is crucial. For instance:

• In HNO89, the structure can be represented as H-O-N=O, with a double bond between N and one O, and a single bond between N and the other O.
• The overall shape is influenced by the bonding pattern, which dictates molecular geometry using principles like VSEPR theory (Valence Shell Electron Pair Repulsion).

Recognizing the molecular structure of a chemical helps predict its behavior, such as how it may interact with other substances or its physical properties.

Resonance

Resonance is a concept that describes the delocalization of electrons within a molecule. When multiple structures can represent a molecule due to electron-pair sharing, the actual distribution is called a resonance hybrid. In the HNO89 molecule, resonance occurs because:

• There are alternate Lewis structures that describe the molecule, illustrating different electron placements while keeping the atom positions the same.
• The true structure is a hybrid of these possible representations, minimizing energy and stabilizing the molecule.

This means that, instead of swapping between states, the electrons are effectively spread across the molecule, impacting its stability and reactivity. Resonance is crucial for understanding the influences of electron distribution on molecular behavior and characteristics.