Problem 217 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following is the wrong statement? \([2013]\) (a) Ozone is violet black in solid state (b) Ozone is diamagnetic gas (c) ONCl and ONO- are isoelectronic (d) \(\mathrm{O}_{3}\) molecule is bent

Step-by-Step Solution

Answer

(c) is incorrect; ONCl and ONO- are not isoelectronic.

Step 1: Analyze Ozone's Properties

The first two options are about ozone. Ozone is indeed violet black in its solid form, so statement (a) is correct. Furthermore, Ozone is a diamagnetic gas because all its electrons are paired, confirming that statement (b) is also correct.

Step 2: Check Isoelectronic Nature of ONCl and ONO-

The option (c) states that ONCl and ONO- are isoelectronic. ONCl consists of 34 electrons (O: 8, N: 7, Cl: 17), while ONO- has 24 electrons (O: 8, N: 7, O: 8, additional electron: 1). Since the electron counts don't match, these molecules are not isoelectronic, making statement (c) incorrect.

Step 3: Examine Structure of \\mathrm{O}_{3}

In option (d), Ozone (\(\mathrm{O}_{3}\)) is mentioned to be bent. The structure of ozone is a resonance hybrid of two structures, with a bond angle of about 117 degrees, confirming statement (d) is correct.

Step 4: Identify the Incorrect Statement

Given the analysis, the only incorrect statement is option (c), as ONCl and ONO- are not isoelectronic.

Key Concepts

Ozone Properties

Ozone, a molecule composed of three oxygen atoms, displays fascinating properties that are important for understanding atmospheric chemistry. In its gaseous state, ozone is both colorless and has a distinctive sharp smell, reminiscent of chlorine. However, when cooled to form a solid, it exhibits a unique violet-black hue. This color is due to the absorption of visible light as it transitions between energy states.
Ozone is also known for its diamagnetic nature. This means it is not attracted to magnetic fields, as all of its electrons are paired. This property contrasts with oxygen gas (O₂), which is paramagnetic due to the presence of unpaired electrons. Such characteristics are crucial for practical applications and detection methods of ozone in various environmental contexts.

Isoelectronic Species

Understanding isoelectronic species involves comparing different chemical species with the same electron count or similar electronic structures. The term "isoelectronic" applies to ions or molecules with an equal number of electrons and, often, a similar arrangement of electrons. These species often exhibit comparable chemical properties.
For instance, the previously considered species ONCl and ONO⁻ were initially thought to be isoelectronic. However, upon calculating their total electron count, ONCl has 34 electrons, while ONO⁻ contains 24 electrons. This mismatch clearly shows they differ in terms of electronic structure, proving they are not isoelectronic. It's important to accurately count the electrons, including those from charges, to verify such relationships.

Molecular Geometry

Molecular geometry focuses on the three-dimensional arrangement of atoms within a molecule. This geometric configuration significantly influences the molecule's physical and chemical properties, such as polarity, color, phase of matter, and reactivity.
Ozone (\(mathrm{O}_{3}\)) serves as a classic example when discussing molecular shapes. It is best described as having a bent shape, with an average bond angle of around 117 degrees. This bent structure results from the molecular resonance, where the position of electrons fluctuates between different states. The bent geometry contributes to ozone's polar nature, causing an unequal distribution of charge and affecting its interaction with other molecules.