CBSE Class 12 (Science) Atoms — practice questions
92 free MCQs with worked solutions. Tap any question for the answer + explanation, or practice them all in the app.
Practice CBSE Class 12 (Science) Atoms in the app →Bohr's postulate quantises the angular momentum of an electron in a stationary orbit asWhich spectral series of hydrogen lies in the visible region of the electromagnetic spectrum?The minimum wavelength $\lambda_{\min}$ in the continuous X-ray spectrum of an X-ray tube depends only onThe ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series of hydrThe radius of the $n$th Bohr orbit in a hydrogen-like atom of nuclear charge $Z$ scales asThe de Broglie wavelength $\lambda$ of an electron in the $n$th Bohr orbit of hydrogen, in terms of the orbit Bohr's quantisation condition for the angular momentum $L$ of an electron in the $n^\text{th}$ orbit isThe ratio of the first excitation energy of a hydrogen atom ($E_2 - E_1$) to its ionisation energy from the grThe first model of the atom was proposed by:Thomson proposed his model of the atom in the year:In Thomson's model, the positive charge is spread:In Thomson's model, electrons are compared to seeds in a:Thomson's model is picturesquely called the:In Rutherford's model, the mass and positive charge sit in the:Rutherford's model compares electrons around the nucleus to:The scattering experiment was carried out in 1911 by Marsden and:Each element emits a spectrum of radiation that is:An atomic gas is usually excited by passing through it an electric:The hydrogen series discovered in 1885 is named after:Which of these is a series in the hydrogen spectrum?Beyond the series limit, the hydrogen spectrum shows a:Bohr set out his theory of the atom in how many postulates?By Bohr's first postulate, an electron in a stable orbit emits:Bohr called the stable non-radiating orbits the:Bohr's second postulate quantises which quantity?Allowed angular momenta are integral multiples of h divided by:By Bohr's third postulate, a transition to lower energy emits a:The energy of the emitted photon equals the difference between the:The lowest energy state of an atom is called the:The ionisation energy of the hydrogen atom is about:In which year did J.J. Thomson put forward the first model of the atom?By what popular name is Thomson's atom model known?Under which scientist did Ernest Rutherford work as a research student?Which two workers carried out the alpha scattering experiment in 1911?Which metal formed the thin foil in the Geiger-Marsden scattering experiment?Scattered alpha particles were detected as flashes on a screen coated with what?About what fraction of alpha particles deflected by more than 90 degrees from gold foil?What percentage of incident alpha particles scattered by more than 1 degree?An alpha particle is the same as the nucleus of which atom?For gold, which atomic number is used when computing the nuclear charge Ze?Why is the gold nucleus treated as stationary in scattering?In alpha scattering, what is the impact parameter?A tiny impact parameter scatters an alpha particle how?What happens to an alpha particle hitting a nucleus head-on?Rutherford's scattering results suggested a nuclear size of about what?From kinetic theory, what was the size of an atom known to be?An atom is roughly how many times larger than its nucleus?Why do most alpha particles pass straight through a thin gold foil?Why do atomic electrons hardly change the path of an alpha particle?A 7.7 MeV alpha particle heads straight at a gold nucleus. What is its closest approach?What is the actual radius of a gold nucleus?Compared with the sum of nuclear and alpha radii, closest approach is?At closest approach, the alpha particle's kinetic energy has become what?Scaled to the atom's proportions, where would Earth orbit the sun?In Rutherford's model, what supplies the electron's centripetal force in hydrogen?What does a negative total energy of an orbiting electron indicate?An electron in hydrogen's ground state has total energy -13.6 eV. What is its kinetic energy?The ground-state orbital radius of the electron in hydrogen is about what?About how fast does the electron move in hydrogen's ground-state orbit?Electron speed 2.2 × 10⁶ m/s, orbit radius 5.3 × 10⁻¹¹ m. Classical light frequency?Classically, what happens to an orbiting electron in Rutherford's atom?What kind of spectrum would a classically spiralling electron emit?What does an emission line spectrum look like?Where do the dark lines of an absorption spectrum fall?Why can an emission line spectrum identify an unknown gas?What did Johann Balmer obtain in 1885 for hydrogen?Bohr's second postulate gives the allowed angular momentum of the electron as what?When an electron drops from energy Ei to a lower Ef, what is the photon frequency?In which year did Bohr present his model of the hydrogen atom?How much energy lifts a hydrogen electron from n = 1 to n = 2?What minimum energy takes hydrogen from its ground state to the second excited state?As n increases, the energy needed to free the electron from the hydrogen atom does what?What is the energy of the hydrogen atom when the electron is removed to infinity at rest?As n grows, how does the spacing between neighbouring hydrogen levels change?The lowest-energy state of an atom, with the electron in the smallest orbit, is called what?Which of these species has only one electron, like hydrogen?Bohr's model fails for which of the following?Which spectral feature of hydrogen can Bohr's model not explain?In modern quantum mechanics, a Bohr orbit is replaced by what?Who explained Bohr's angular momentum quantisation using the wave nature of the electron?In which year did Davisson and Germer verify the wave nature of electrons?Which condition lets a de Broglie electron orbit persist?How many de Broglie wavelengths fit around the n = 3 Bohr orbit?What is the orbital angular momentum of the electron in the n = 2 Bohr orbit?The n = 3 orbit of hydrogen has what radius compared with the n = 1 orbit?A hydrogen electron falls from n = 3 to n = 2. What photon energy is emitted?In which region of the spectrum does the Lyman series of hydrogen lie?Balmer series lines arise when the electron falls to which level?Which spectral region contains the Paschen series of hydrogen?The hydrogen series ending at n = 1 is named after which physicist?Which hydrogen series ends on the n = 4 level?Which hydrogen series, ending at n = 6, was discovered in 1953?