Modern Physics - Atoms
Q. In the context of atomic structure, what does the term 'isotope' refer to? (2021)
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A.
Atoms with the same number of protons but different neutrons
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B.
Atoms with different numbers of protons
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C.
Atoms with the same mass number
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D.
Atoms that are chemically identical
Solution
Isotopes are defined as atoms that have the same number of protons but different numbers of neutrons.
Correct Answer: A — Atoms with the same number of protons but different neutrons
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Q. What is the energy of a photon emitted when an electron transitions from n=4 to n=2 in a hydrogen atom? (2019)
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A.
10.2 eV
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B.
12.1 eV
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C.
1.89 eV
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D.
3.4 eV
Solution
The energy difference can be calculated using the formula E = 13.6 eV (1/n1² - 1/n2²). For n1=2 and n2=4, E = 13.6(1/2² - 1/4²) = 10.2 eV.
Correct Answer: A — 10.2 eV
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Q. What is the main limitation of the Rutherford model of the atom? (2019)
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A.
It does not explain the stability of atoms
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B.
It does not account for neutrons
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C.
It cannot explain spectral lines
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D.
It does not include electrons
Solution
The Rutherford model fails to explain why electrons do not spiral into the nucleus, thus not accounting for atomic stability.
Correct Answer: A — It does not explain the stability of atoms
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Q. What is the maximum number of electrons that can occupy the n=3 energy level in an atom? (2021)
Solution
The maximum number of electrons in an energy level is given by the formula 2n². For n=3, it is 2(3)² = 18.
Correct Answer: C — 18
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Q. Which of the following quantum numbers describes the shape of an atomic orbital? (2022)
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A.
Principal quantum number
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B.
Azimuthal quantum number
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C.
Magnetic quantum number
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D.
Spin quantum number
Solution
The azimuthal quantum number (l) describes the shape of the atomic orbital.
Correct Answer: B — Azimuthal quantum number
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