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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:
Assertion : Isotopes of an element show different valencies.
Reason : Isotopes have different atomic numbers.
- a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).
- b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).
- c)Assertion (A) is true but reason (R) is false.
- d)Both A and R are False
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
Direction: In the following questions, a statement of assertion (A) is...
Isotopes have the same number of electrons. Hence, their valencies do not differ. Isotopes have the same atomic number but different atomic mass numbers: The total number of protons present in the atomic nucleus is known as its atomic number whereas the mass number is defined as the total number of protons and neutrons present in the atomic nucleus.
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Direction: In the following questions, a statement of assertion (A) is...
Assertion: Isotopes of an element show different valencies.
Reason: Isotopes have different atomic numbers.
The correct answer is option 'D', which states that Assertion (A) is false but Reason (R) is true.
Explanation:
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means that isotopes have the same atomic number (number of protons) but different mass numbers (sum of protons and neutrons).
Valency:
Valency is the combining capacity of an element, which determines the number of electrons an atom can gain, lose, or share in order to achieve a stable electron configuration. It depends on the number of valence electrons an atom possesses.
Assertion (A): Isotopes of an element show different valencies.
This statement is incorrect. Isotopes of an element have the same number of valence electrons because they have the same atomic number. Valency is determined by the number of valence electrons, which remains the same for isotopes of the same element.
Reason (R): Isotopes have different atomic numbers.
This statement is true. Isotopes have different atomic numbers because they have different numbers of neutrons. The atomic number represents the number of protons in an atom, and since isotopes have different numbers of neutrons, their atomic numbers will be different.
Conclusion:
The reason (R) is true because isotopes do have different atomic numbers. However, the assertion (A) is false because isotopes of an element show the same valency since they have the same number of valence electrons. Therefore, option 'D' is the correct answer.
Reason: Isotopes have different atomic numbers.
The correct answer is option 'D', which states that Assertion (A) is false but Reason (R) is true.
Explanation:
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means that isotopes have the same atomic number (number of protons) but different mass numbers (sum of protons and neutrons).
Valency:
Valency is the combining capacity of an element, which determines the number of electrons an atom can gain, lose, or share in order to achieve a stable electron configuration. It depends on the number of valence electrons an atom possesses.
Assertion (A): Isotopes of an element show different valencies.
This statement is incorrect. Isotopes of an element have the same number of valence electrons because they have the same atomic number. Valency is determined by the number of valence electrons, which remains the same for isotopes of the same element.
Reason (R): Isotopes have different atomic numbers.
This statement is true. Isotopes have different atomic numbers because they have different numbers of neutrons. The atomic number represents the number of protons in an atom, and since isotopes have different numbers of neutrons, their atomic numbers will be different.
Conclusion:
The reason (R) is true because isotopes do have different atomic numbers. However, the assertion (A) is false because isotopes of an element show the same valency since they have the same number of valence electrons. Therefore, option 'D' is the correct answer.
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Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer? for Class 9 2026 is part of Class 9 preparation. The Question and answers have been prepared according to the Class 9 exam syllabus. Information about Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 9 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer?.
Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer? for Class 9 2026 is part of Class 9 preparation. The Question and answers have been prepared according to the Class 9 exam syllabus. Information about Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 9 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Direction: In the following questions, a statement of assertion (A) is followed by a statement of reason (R). Mark the correct choice as:Assertion : Isotopes of an element show different valencies.Reason : Isotopes have different atomic numbers.a)Both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).b)Both assertion (A) and reason (R) are true but reason (R) is not the correct explanation of assertion (A).c)Assertion (A) is true but reason (R) is false.d)Both A and R are FalseCorrect answer is option 'D'. Can you explain this answer?.
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