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JEE Main Unit 1B1: Atomic Structure & Quantum Mechanics — practice questions

Explore 24 free Unit 1B1: Atomic Structure & Quantum Mechanics questions in JEE Main Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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Unit 1B1: Atomic Structure & Quantum Mechanics questions and exercises with answers

Showing questions 1–24 of 24.

Bohr's first postulate: electrons revolve in ___ orbits around the nucleus.Read the answer and worked solution →In Bohr's model, angular momentum of an electron in orbit n equals:Read the answer and worked solution →Energy of electron in n-th orbit of hydrogen:Read the answer and worked solution →Principal quantum number n indicates:Read the answer and worked solution →Number of orbitals in subshell of azimuthal quantum number l:Read the answer and worked solution →How many electrons can fit in a single orbital?Read the answer and worked solution →Electron configuration of carbon (Z = 6):Read the answer and worked solution →For hydrogen, wavelength emitted in n=3 to n=2 transition (Balmer):Read the answer and worked solution →de Broglie wavelength of an electron with momentum p:Read the answer and worked solution →Heisenberg uncertainty principle:Read the answer and worked solution →Number of subshells in shell with n = 3:Read the answer and worked solution →Electron configuration of nitrogen (Z = 7):Read the answer and worked solution →Total number of electrons that can occupy shell with n = 4:Read the answer and worked solution →Magnetic quantum number m_l for a 3d orbital can be:Read the answer and worked solution →Wavelength of light needed to ionize hydrogen from ground state (13.6 eV):Read the answer and worked solution →Radius of n-th Bohr orbit for hydrogen (a₀ ≈ 0.529 Å):Read the answer and worked solution →Effective nuclear charge Z_eff for the 2p electron of carbon (using Slater's rules approximately):Read the answer and worked solution →For He⁺ ion (1 electron, Z = 2), energy in ground state:Read the answer and worked solution →The Pauli exclusion principle states that two electrons in an atom cannot have:Read the answer and worked solution →Energy of the photon emitted in a hydrogen transition from n=4 to n=2:Read the answer and worked solution →Number of nodes in a 3p orbital (n=3, l=1):Read the answer and worked solution →For Bohr's hydrogen-like atom, what is the velocity of electron in n-th orbit (in terms of fine structure constant α and c)?Read the answer and worked solution →Photoelectric effect: when light of frequency ν falls on a metal of work function φ, KE of emitted electrons is:Read the answer and worked solution →Which Bohr orbit energy is higher (less negative)?Read the answer and worked solution →

Worked practice questions

Bohr's first postulate: electrons revolve in ___ orbits around the nucleus.

  1. Spiral
  2. Specific (quantized) energy orbits
  3. Linear
  4. Random
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Correct answer: B. Specific (quantized) energy orbits

Bohr postulated that electrons can only exist in specific 'stationary' orbits with quantized energies. In these orbits they don't radiate energy, contrary to classical EM theory. Resolves the atomic stability problem.

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In Bohr's model, angular momentum of an electron in orbit n equals:

  1. n h
  2. h / n
  3. 2 h / n
  4. n h / (2π) (= nħ)
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Correct answer: D. n h / (2π) (= nħ)

**Bohr's quantization condition:** L = nh/(2π) = nħ for orbit n. Only specific values allowed. Foundation of quantum mechanics.

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Energy of electron in n-th orbit of hydrogen:

  1. E_n = +13.6 n²
  2. E_n = -13.6/n² eV
  3. E_n = h × n
  4. E_n = -n²
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Correct answer: B. E_n = -13.6/n² eV

E_n = -13.6/n² eV (for hydrogen). Negative because electron is bound. Goes to 0 as n → infinity (free electron at infinity).

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