Which of the following statements about molecules of elements is correct?

RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Biochemistry and Nutrition

Easy

Appeared in: RRB Nsg. Superintendent - 29 April 2025 (Shift-3rd)

Explanation

Molecular oxygen (O₂) and ozone (O₃) are different molecular forms of the same element, which is oxygen.
These different forms are known as allotropes, which are different structural modifications of an element in the same physical state.
Since both molecules are composed exclusively of oxygen atoms, the statement is correct.

Option B: Many elements exist as diatomic (e.g., O₂, N₂) or polyatomic (e.g., S₈) molecules in nature.
Option C: Diatomic molecules can be composed of atoms of the same element (homonuclear), such as oxygen (O₂) and nitrogen (N₂).
Option D: The most common molecular form of phosphorus is white phosphorus, which is a tetra-atomic molecule (P₄), containing four atoms.

Visual 1: Diagram - An illustration comparing the molecular structure of O₂ (a linear two-atom molecule) and O₃ (a bent three-atom molecule), emphasizing that both are made of oxygen atoms.
Visual 2: Table - A chart categorizing elements by their natural atomicity, with columns for Monoatomic (e.g., He, Ar), Diatomic (e.g., H₂, O₂, Cl₂), and Polyatomic (e.g., P₄, S₈).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Properties of molecules and elements, including allotropes and atomicity as background academic context rather than a clinical decision trigger.
Understanding the distinction between allotropes like molecular oxygen (O₂) and ozone (O₃) is vital in a clinical context. O₂ is essential for cellular respiration and life, whereas O₃ is a toxic gas that can cause severe respiratory damage.
This basic chemistry knowledge is foundational for understanding pharmacology and the behavior of different elements and compounds within the body.
What if? If a nurse were to administer a gas mixture, confusing different allotropes could be fatal. For example, administering ozone instead of medical-grade oxygen would lead to lung tissue destruction instead of supporting respiration.

How to Approach the Question

Step 1: Identify the core task: find the one correct statement among the four options about molecules and elements.
Step 2: Analyze Option A. Recall the formulas for molecular oxygen (O₂) and ozone (O₃). Both are composed of oxygen atoms. This makes them different molecular forms (allotropes) of the same element. The statement is correct.
Step 3: Analyze Option B. Recall that while noble gases are monoatomic, many common elements like hydrogen, nitrogen, and oxygen are diatomic (H₂, N₂, O₂). The word 'All' makes this statement false.
Step 4: Analyze Option C. Recall examples of diatomic molecules. O₂ consists of two atoms of the same element. CO consists of two atoms of different elements. The word 'only' makes this statement false.
Step 5: Analyze Option D. Recall the common form of phosphorus, which is white phosphorus (P₄). It contains four atoms, not five. This statement is false.
Step 6: Conclude that Option A is the only correct statement.

Concept Tested & Keywords

Concept Tested: Properties of molecules and elements, including allotropes and atomicity.
Stem keywords: molecules of elements, correct statement
Lead-in keywords: correct
Negative lead-in flag: false

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