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OJEE Atoms — practice questions

Explore 31 free Atoms questions in OJEE Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Atoms questions and exercises with answers

Showing questions 1–30 of 31.

According to the Bohr model, the ground-state energy of a hydrogen atom is:Read the answer and worked solution →Bohr's postulate quantises the angular momentum of an electron in a stationary orbit asRead the answer and worked solution →Which spectral series of hydrogen lies in the visible region of the electromagnetic spectrum?Read the answer and worked solution →The minimum wavelength $\lambda_{\min}$ in the continuous X-ray spectrum of an X-ray tube depends only onRead the answer and worked solution →The ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series of hydrogen isRead the answer and worked solution →The radius of the $n$th Bohr orbit in a hydrogen-like atom of nuclear charge $Z$ scales asRead the answer and worked solution →The de Broglie wavelength $\lambda$ of an electron in the $n$th Bohr orbit of hydrogen, in terms of the orbit radius $r_n$, isRead the answer and worked solution →Trace how an X ray tube firesRead the answer and worked solution →Order the atomic models in this chapterRead the answer and worked solution →True or false: Rutherford's two difficultiesRead the answer and worked solution →Which model does this belong to?Read the answer and worked solution →Complete Bohr's first postulateRead the answer and worked solution →True or false: line spectraRead the answer and worked solution →Charge and neutralityRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Tap every problem Bohr's model was built to solveRead the answer and worked solution →Flip and pair: model with its pictureRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Strength or weakness?Read the answer and worked solution →Complete the size of the nucleusRead the answer and worked solution →Reading the models backRead the answer and worked solution →Bohr's postulatesRead the answer and worked solution →Explained, or left unexplained?Read the answer and worked solution →True or false: the nucleusRead the answer and worked solution →Order the argument: why Rutherford's atom should collapseRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Assertion and reason: modelsRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →

Worked practice questions

According to the Bohr model, the ground-state energy of a hydrogen atom is:

  1. $-13.6$ eV
  2. $-6.8$ eV
  3. $-27.2$ eV
  4. $-3.4$ eV
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Correct answer: A. $-13.6$ eV

Bohr's energy formula: $E_n = -\dfrac{13.6}{n^2}$ eV for hydrogen. For the ground state $n = 1$: $E_1 = -13.6$ eV. - Option A ($-3.4$ eV) is $E_2$. - Option D ($-27.2$ eV) is the magnitude of *twice* the ground-state energy (a common confusion with the virial-theorem relation $E = -\frac{1}{2}|U|$).

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Bohr's postulate quantises the angular momentum of an electron in a stationary orbit as

  1. $L = \tfrac{\hbar}{n}$
  2. $L = nh^2$
  3. $L = n\hbar$
  4. $L = nh$
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Correct answer: C. $L = n\hbar$

Bohr postulated $L = mvr = n\hbar = \tfrac{nh}{2\pi}$ for positive integers $n$. **Option A is off by a factor of $2\pi$ — a classic distractor.**

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Which spectral series of hydrogen lies in the visible region of the electromagnetic spectrum?

  1. Paschen
  2. Pfund
  3. Lyman
  4. Balmer
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Correct answer: D. Balmer

Balmer (transitions to $n=2$) covers wavelengths roughly $364\,\text{nm}$ to $656\,\text{nm}$ — the visible band. Lyman is UV (transitions to $n=1$), Paschen and Pfund are infrared (to $n=3$ and $n=5$).

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