Isobars of elements have same :
- A.Atomic numbers.
- B.Number of electrons.
- C.Mass numbers.
- D.Number of neutrons.
Correct answer
Explanation
The correct answer is C, Mass numbers. Isobars are atoms of different elements that have the same mass number but different atomic numbers. The mass number is the total of protons and neutrons in the nucleus, so isobars have the same number of nucleons arranged differently: more protons and fewer neutrons in one, the reverse in another. A standard example is argon-40, potassium-40 and calcium-40, with atomic numbers 18, 19 and 20 but the same mass number, 40. Carbon-14 and nitrogen-14 are another pair. Because their atomic numbers differ, isobars are different elements with different chemical properties. Option A is wrong because atoms with the same atomic number but different mass numbers are isotopes, such as carbon-12 and carbon-14. Option B is wrong because a neutral atom has as many electrons as protons, so isobars, having different atomic numbers, also have different numbers of electrons. Option D is wrong because atoms with the same number of neutrons are isotones, such as carbon-14 and oxygen-16. Exam tip: isotopes share protons, isobars share mass number, isotones share neutrons.
Practice Questions
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- A.Thomas Savery
- B.Thomas Newcomen
- C.James Watt
- D.Richard Arkwright
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- A.20 Ω
- B.10 Ω
- C.5 Ω
- D.15 Ω
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- A.nearby object is focused beyond the retina.
- B.nearby object is focused before the retina.
- C.distant object is focused before the retina.
- D.distant object is focused beyond the retina.
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Read the full explanation →A homogeneous mixture contains two liquids. How are they separated ?
- A.By filtration
- B.By evaporation
- C.By distillation
- D.By condensation
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Read the full explanation →Cartilage is NOT found in
- A.larynx
- B.nose
- C.ear
- D.urinary bladder
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