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Chemistry Chapter 3 : Topic 11
Isotopes
1 / 20
Which of the following statements correctly defines isotopes?
Reasoning: Isotopes are atoms of the same element, so they must have the same atomic number (protons), but they differ in neutrons, leading to different mass numbers.
2 / 20
Three atoms of chlorine are given:
Reasoning: All have the same atomic number (17 protons), so they are isotopes differing in neutrons.
3 / 20
An atom has 6 protons, 6 electrons, and 8 neutrons. Another atom has 6 protons, 6 electrons, and 6 neutrons. These atoms are:
Reasoning: Same number of protons means same element (carbon), but different neutrons makes them isotopes.
4 / 20
Which pair represents isotopes of hydrogen?
Reasoning: Protium, Deuterium, and Tritium are isotopes of hydrogen differing in neutron number.
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Which statement best explains why isotopes have similar chemical properties?
Reasoning: Chemical properties depend on electron configuration, which is the same in isotopes.
6 / 20
Carbon-12 and Carbon-14 differ in:
Reasoning: Both have 6 protons, but Carbon-12 has 6 neutrons while Carbon-14 has 8 neutrons.
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Which of the following is NOT true about isotopes?
Reasoning: Isotopes always have the same number of protons; otherwise, they would be different elements.
8 / 20
An element X has isotopes X-10 and X-11. What causes the difference between them?
Reasoning: topes differ only in neutron number, affecting mass number.
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Which statement correctly describes isotopes in terms of physical properties?
Reasoning: Physical properties like density and mass differ slightly due to neutron variation.
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Which of the following represents correct reasoning for isotopes of an element?
Reasoning: Atomic number defines element identity; isotopes differ in mass number only.
11 / 20
A student says: “All atoms of oxygen must have the same mass.” This statement is:
Reasoning: Oxygen has isotopes like O-16, O-17, and O-18 with different neutron numbers.
12 / 20
Which combination correctly shows isotopes?
Reasoning: Both are carbon atoms with same atomic number but different mass numbers.
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What is the main reason isotopes are placed in the same position in the periodic table?
Reasoning: Periodic table arrangement is based on atomic number, which is same for isotopes.
14 / 20
Which statement about isotopes is correct?
Reasoning: Isotopes differ only in neutrons while protons and electrons remain same.
15 / 20
A neutral atom has atomic number 8 and mass number 18. How many neutrons does it contain?
Reasoning: Neutrons = Mass number - Atomic number =18-8=10
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Which feature is responsible for the identity of an element and remains unchanged in isotopes?
Reasoning: Atomic number (protons) defines the element and remains constant in isotopes.
17 / 20
Why do isotopes have different atomic masses?
Reasoning: Neutrons contribute to mass number; variation in neutrons changes atomic mass.
18 / 20
Which of the following is a correct comparison of isotopes?
Reasoning: Isotopes behave similarly chemically but differ slightly in physical properties.
19 / 20
If two atoms have the same atomic number but different mass numbers, they must be:
Reasoning: Same atomic number confirms same element; different mass numbers indicate isotopes.
20 / 20
Which of the following best explains the concept of isotopes in a real-world context?
Reasoning: Isotopes show that an element can exist in different mass forms while maintaining chemical identity.
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