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UPCET / UPSEE Atoms and Nuclei — practice questions

Explore 26 free Atoms and Nuclei questions in UPCET / UPSEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Atoms and Nuclei questions and exercises with answers

Showing questions 1–26 of 26.

Atomic number Z is:Read the answer and worked solution →Mass number A is:Read the answer and worked solution →Isotopes have:Read the answer and worked solution →Bohr's first orbit radius for hydrogen:Read the answer and worked solution →In hydrogen atom, energy of n-th orbit:Read the answer and worked solution →Lyman series transitions land at n = ___, lying in:Read the answer and worked solution →Rydberg formula for hydrogen lines:Read the answer and worked solution →Half-life of radioactive sample is T₁/₂. Decay constant λ:Read the answer and worked solution →Number of atoms remaining after 3 half-lives:Read the answer and worked solution →Binding energy per nucleon for ⁵⁶Fe:Read the answer and worked solution →Atomic mass unit u corresponds to energy:Read the answer and worked solution →β⁻ decay: a neutron in nucleus converts to:Read the answer and worked solution →Activity of N nuclei with decay constant λ:Read the answer and worked solution →Half-life of ¹⁴C is 5730 years. Sample with 25% original activity is:Read the answer and worked solution →Energy released in fusion: 4 protons → He-4 + 2 e⁺ + 2 ν_e (solar fusion). About:Read the answer and worked solution →Wavelength of de Broglie wave of electron in n-th Bohr orbit:Read the answer and worked solution →Nuclear radius R relates to mass number A as:Read the answer and worked solution →For ¹H ground state to first excited state (n=2), photon required:Read the answer and worked solution →Mass-energy equivalence: rest energy of electron (m_e = 9.11 × 10⁻³¹ kg):Read the answer and worked solution →Activity of 1 gram of ²²⁶Ra (Avogadro = 6 × 10²³; T₁/₂ = 1600 yr):Read the answer and worked solution →In a hydrogen atom transition from n=4 to n=2, the emitted photon belongs to:Read the answer and worked solution →For He⁺ ion (Z = 2), energy of n=1 (ground state):Read the answer and worked solution →Mean lifetime τ of radioactive nucleus vs half-life T₁/₂:Read the answer and worked solution →Merge halves back to a full sampleRead the answer and worked solution →Tap what belongs to the nucleusRead the answer and worked solution →Which one does NOT belong?Read the answer and worked solution →

Worked practice questions

Atomic number Z is:

  1. Mass number
  2. Number of PROTONS in nucleus
  3. Random
  4. Number of nucleons
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Correct answer: B. Number of PROTONS in nucleus

Z = number of protons (also = number of electrons in neutral atom). Determines element identity. Z = 1 (H), 2 (He), 6 (C), etc.

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Mass number A is:

  1. Atomic mass
  2. Number of PROTONS + NEUTRONS (= Z + N)
  3. Charge
  4. Number of electrons
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Correct answer: B. Number of PROTONS + NEUTRONS (= Z + N)

A = Z + N (nucleons total). Notation ^A_Z X: e.g., ^12_6 C has 6 protons + 6 neutrons ^14_6 C has 6 protons + 8 neutrons (carbon-14 isotope).

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Isotopes have:

  1. Different element
  2. Same N
  3. Same Z (same element), different A (different N)
  4. Same A, different Z
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Correct answer: C. Same Z (same element), different A (different N)

**Isotopes:** same Z (same element), different mass number A. Examples: ¹H, ²H (deuterium), ³H (tritium); ¹²C and ¹⁴C. Chemically identical, physically different (mass).

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