Consider the following statements regarding the molecule of a compound. Which of the following statements is/are correct?

Statement 1: A molecule of a compound must consist of atoms of at least two different elements.

Statement 2: Ozone $(\mathrm{O}_3)$ is a molecule of a compound because it contains multiple oxygen atoms.

1. A

   Only Statement 2 is correct

2. B

   Neither Statement 1 nor 2 is correct

3. C

   Only Statement 1 is correct

4. D

   Both Statements 1 and 2 are correct

Appeared in: RRB Nsg. Superintendent -29 April-2025 (shift-2nd)

Explanation

• Statement 1 is correct as it provides the fundamental definition of a molecule of a compound.
• A compound, by definition, is a chemical substance composed of many identical molecules containing atoms from more than one chemical element held together by chemical bonds.
• For example, a water molecule (H₂O) is a compound because it contains atoms of two different elements: hydrogen and oxygen.
• Conversely, a molecule containing atoms of only one element, like molecular oxygen (O₂), is a molecule of an element, not a compound.

Why Other Options Were Wrong

• Option A: This option is incorrect because Statement 2 is false. Ozone (O₃) is a molecule of the element oxygen, as it is composed solely of oxygen atoms. A compound requires atoms from at least two different elements.
• Option B: This option is incorrect because Statement 1 is a true and accurate definition of a molecule of a compound.
• Option D: This option is incorrect because while Statement 1 is true, Statement 2 is false. Ozone (O₃) is an allotrope of the element oxygen, not a compound.

Related Visual

• Visual 1: Diagram - An illustration comparing an atom (e.g., a single sphere for O), a molecule of an element (e.g., three connected spheres for O₃), and a molecule of a compound (e.g., one large sphere connected to two smaller spheres for H₂O). This visual clarifies the structural differences based on atomic composition.

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Distinction between molecules of elements and molecules of compounds as background academic context rather than a clinical decision trigger.
• Understanding the difference between elements and compounds is foundational for nursing pharmacology and physiology. For instance, administering oxygen (O₂, an element) for respiratory support is distinct from administering nitrous oxide (N₂O, a compound) as an anesthetic.
• This basic chemistry knowledge is crucial for comprehending drug compositions, metabolic pathways (e.g., the breakdown of glucose, a compound), and the function of electrolytes (which are ions of elements) in maintaining homeostasis.
• What if? If a molecule contained only two atoms of oxygen (O₂), it would still be a molecule of the element oxygen, not a compound. Its role in respiration is vital, whereas the properties of ozone (O₃), another molecule of the same element, are toxic when inhaled.

How to Approach the Question

• Step 1: Carefully read and analyze each statement individually to understand the claim being made.
• Step 2: Recall the precise scientific definitions of 'element' and 'compound'. An element consists of only one type of atom, while a compound consists of two or more different types of atoms chemically bonded.
• Step 3: Evaluate Statement 1. It claims a compound's molecule must have atoms of at least two different elements. This aligns perfectly with the definition of a compound.
• Step 4: Evaluate Statement 2. It claims Ozone (O₃) is a compound because it has multiple atoms. Analyze the composition of O₃. It contains only oxygen atoms. A substance with only one type of atom is an element, regardless of how many atoms are in its molecule. Thus, Statement 2 is incorrect.
• Step 5: Conclude that only Statement 1 is correct and select the option that reflects this conclusion.

Concept Tested & Keywords

• Concept Tested: Distinction between molecules of elements and molecules of compounds
• Stem keywords: molecule, compound, atoms, elements, Ozone, O3
• Lead-in keywords: correct
• Negative lead-in flag: false

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