A model for quantized motion of an electron in a uniform magnetic field \(B\) states that the flux passing through the orbit of the electron is \(n(h/e)\) where \(n\) is an integer, \(h\) is Planck's constant and \(e\) is the magnitude of electron's charge. According to the model, the magnetic moment of an electron in its lowest energy state will be (\(m\) is the mass of the electron)
Atoms and Nuclei
Every question from past board papers on Atoms and Nuclei, newest paper first. Open any question for its full worked answer.
NEET UG 2025 question paper (official, booklet 45)
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A particle of mass \(m\) is moving around the origin with a constant force \(F\) pulling it towards the origin. If Bohr model is used to describe its motion, the radius \(r\) of the \(n^{th}\) orbit and the particle's speed \(v\) in the orbit depend on \(n\) as
NEET UG 2024 question paper (official, booklet S6)
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Match List I with List II.
List I (Spectral Lines of Hydrogen for transitions from): A. \(n_2=3\) to \(n_1=2\); B. \(n_2=4\) to \(n_1=2\); C. \(n_2=5\) to \(n_1=2\); D. \(n_2=6\) to \(n_1=2\)
List II (Wavelengths (nm)): I. 410.2; II. 434.1; III. 656.3; IV. 486.1
Choose the correct answer from the options given below :
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Given below are two statements :
Statement I : Atoms are electrically neutral as they contain equal number of positive and negative charges.
Statement II : Atoms of each element are stable and emit their characteristic spectrum.
In the light of the above statements, choose the most appropriate answer from the options given below :
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\({}^{290}_{82}X \xrightarrow{\alpha} Y \xrightarrow{e^+} Z \xrightarrow{\beta^-} P \xrightarrow{e^-} Q\)
In the nuclear emission stated above, the mass number and atomic number of the product \(Q\) respectively, are :
NEET UG 2023 question paper (official, booklet G6)
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In hydrogen spectrum, the shortest wavelength in the Balmer series is \(\lambda\). The shortest wavelength in the Bracket series is :
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The half life of a radioactive substance is 20 minutes. In how much time, the activity of substance drops to \(\left(\frac{1}{16}\right)^{th}\) of its initial value?
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The radius of inner most orbit of hydrogen atom is \(5.3\times10^{-11}\) m. What is the radius of third allowed orbit of hydrogen atom?
NEET UG 2022 question paper (official, booklet R6)
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In the given nuclear reaction, the element X is :
\({}^{22}_{11}\text{Na} \rightarrow X + e^{+} + \nu\)
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Let \(T_1\) and \(T_2\) be the energy of an electron in the first and second excited states of hydrogen atom, respectively. According to the Bohr's model of an atom, the ratio \(T_1 : T_2\) is :
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A nucleus of mass number 189 splits into two nuclei having mass number 125 and 64. The ratio of radius of two daughter nuclei respectively is :
NEET UG 2021 question paper (official, booklet M4)
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A radioactive nucleus \(^A_ZX\) undergoes spontaneous decay in the sequence
\(^A_ZX \to {}_{Z-1}B \to {}_{Z-3}C \to {}_{Z-2}D\), where Z is the atomic number of element X. The possible decay particles in the sequence are :
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The half-life of a radioactive nuclide is 100 hours. The fraction of original activity that will remain after 150 hours would be :
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A nucleus with mass number 240 breaks into two fragments each of mass number 120, the binding energy per nucleon of unfragmented nuclei is 7.6 MeV while that of fragments is 8.5 MeV. The total gain in the Binding Energy in the process is :
NEET UG 2020 question paper (official, booklet E1)
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For which one of the following, Bohr model is not valid ?
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The energy equivalent of 0.5 g of a substance is :
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When a uranium isotope \(^{235}_{92}\)U is bombarded with a neutron, it generates \(^{89}_{36}\)Kr, three neutrons and :
NEET UG 2019 question paper (official, booklet P1)
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The total energy of an electron in an atom in an orbit is \(-3.4\) eV. Its kinetic and potential energies are, respectively :
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\(\alpha\)-particle consists of :
NEET UG 2018 question paper (official, booklet EE)
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For a radioactive material, half-life is 10 minutes. If initially there are 600 number of nuclei, the time taken (in minutes) for the disintegration of 450 nuclei is
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The ratio of kinetic energy to the total energy of an electron in a Bohr orbit of the hydrogen atom, is
NEET UG 2017 question paper (official, booklet B)
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Radioactive material 'A' has decay constant '8\(\lambda\)' and material 'B' has decay constant '\(\lambda\)'. Initially they have same number of nuclei. After what time, the ratio of number of nuclei of material 'B' to that 'A' will be \(\frac{1}{e}\) ?
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The ratio of wavelengths of the last line of Balmer series and the last line of Lyman series is :
NEET UG 2016 Phase 1 question paper (official, booklet A)
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When an \(\alpha\)-particle of mass 'm' moving with velocity 'v' bombards on a heavy nucleus of charge 'Ze', its distance of closest approach from the nucleus depends on m as :
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Given the value of Rydberg constant is \(10^{7}\ m^{-1}\), the wave number of the last line of the Balmer series in hydrogen spectrum will be :
NEET UG 2016 Phase 2 question paper (official, booklet ZZ)
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If an electron in a hydrogen atom jumps from the 3rd orbit to the 2nd orbit, it emits a photon of wavelength \(\lambda\). When it jumps from the 4th orbit to the 3rd orbit, the corresponding wavelength of the photon will be
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The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is