JEE Chemistry Structure of Atoms MCQs B

Question. Which of the scientist were able to prove that atom is no longer non-divisible?
(a) Michael Faraday
(b) Chadwick
(c) Dalton
(d) Thomson

Answer: A

Question. Which of the following is never true for cathode rays ?
(a) They are electromagnetic waves
(b) They possess kinetic energy.
(c) They produce heat
(d) They produce mechanical pressure

Answer: A

Question. Cathode rays are deflected by
(a) by both
(b) an electric field only
(c) magnetic field only
(d) by none

Answer: A

Question. Which of the following statement is not correct about the characteristics of cathode rays?
(a) Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube
(b) Characteristics of cathode rays do not depend upon the material of electrodes in cathode ray tube
(c) They travel in straight line in the absence of an externalelectrical or magnetic field
(d) They start from the cathode and move towards the anode

Answer: A

Question. Which of the following statements about the electron is incorrect?
(a) The mass of electron is equal to the mass of neutron
(b) It is negatively charged particle
(c) It is a basic constituent of all atoms
(d) None of these

Answer: A

Question. While performing cathode ray experiments, it was observed that there was no passage of electric current under normal conditions. Which of the following can account for this observation ?
(a) Air is a poor conductor of electricity under normal conditions
(b) None of the above
(c) Carbon dioxide is present in air
(d) Dust particles are present in air

Answer: A

Question. Which is not true with respect to cathode rays?
(a) Move with speed same as that of light
(b) Charged particles
(c) A stream of electrons
(d) Can be deflected by magnetic fields

Answer: A

Question. What is the optimum conditions required to study the conduction of electricity through gases
(a) Low pressure and high voltage
(b) High pressure and high voltage
(c) High pressure and low voltage
(d) Low pressure and low voltage

Answer: A

Question. In discharge tube experiment stream of negatively charged particles travel from
(a) cathode to anode
(b) Electrons does not travel
(c) anode to cathode
(d) None of these

Answer: A

Question. Millikan performed an experiment method to determine which of the following ?
(a) Charge of the electron
(b) Mass of the electron
(c) e/m ratio of electron
(d) None of these

Answer: A

Question. The discovery of neutron became very late because
(a) neutrons are chargeless
(b) neutrons are present in nucleus
(c) neutrons are fundamental particles
(d) all of the above

Answer: A

Question. Which is correct statement about proton ?
(a) neutron
(b) positron
(c) None of these
(d) proton

Answer: A

Question. When beryllium is bombarded with alpha particles (Chadwick’s experiment) extremely penetrating radiations, Which cannot be deflected by electrical or magnetic field are given out. These are :
(a) A beam of neutrons
(b) Alpha rays
(c) A beam of protons
(d) A beam of neutrons and protons

Answer: A

Question. Neutron is discovered by
(a) Chadwick
(b) Yukawa
(c) Rutherford
(d) Dalton

Answer: A

Question. Which of the following properties of atom could be explained correctly by Thomson Model of atom?
(a) Overall neutrality of atom
(b) Spectra of hydrogen atom
(c) Position of electrons, protons and neutrons in atom
(d) Stability of atom

Answer: A

Question. When atoms are bombarded with alpha particles, only, a few in million suffer deflection, others pass out undeflected. This is because
(a) the nucleus occupies much smaller volume compared to the volume of the atom
(b) there is only one nucleus and large number of electrons
(c) the force of attraction between alpha particle and oppositely charged electrons is very small
(d) the force of repulsion on the moving alpha particle is small

Answer: A

Question. Rutherford’s experiment which established the nuclear model of the atom used a beam of
(a) helium nuclei, which impinged on a metal foil and got scattered
(b) helium atoms, which impinged on a metal foil and got scattered
(c) Both
(d) None of these

Answer: A

Question. Which of the following scientists explained his model on the basis of centrifugal force ?
(a) Rutherford
(b) Dalton
(c) Thomson
(d) Millikan

Answer: A

Question. The number of neutrons in dipositive zinc ion with mass number 70 is
(a) 40
(b) 36
(c) 34
(d) 38

Answer: A

Question. An element has atomic number 11 and mass number 24. What does the nucleus contain?
(a) 11 protons, 13 neutrons
(b) 11 protons, 13 neutrons, 13 electrons
(c) 13 protons, 11 neutrons
(d) 13 protons, 11 electrons

Answer: A

Question. The number of electrons and neutrons of an element is 18 and 20 respectively. Its mass number is
(a) 38
(b) 17
(c) 2
(d) 37

Answer: A

Question. Nucleons are
(a) neutrons + protons
(b) only neutrons
(c) neutrons + protons + electrons
(d) neutrons + electrons

Answer: A

Question. Atoms with same mass number but different atomic numbers are called
(a) isobars
(b) None of these
(c) isotopes
(d) isochores

Answer: A

Question. What is the difference between two species if one has atomic mass = 14 and atomic number = 7 whereas the other has atomic mass = 14 and atomic number = 6 ?
(a) All of these
(b) Protons
(c) Neutrons
(d) Electrons

Answer: A

Question. If the wavelength of the electromagnetic radiation is increased to thrice the digital value, then what will be the percent change in the value of frequency of the electromagnetic radiation.
(a) Decreases by 66%
(b) Decreases by 33%
(c) Increases by 33%
(d) Increases by 66%

Answer: A

Question. The ideal body, which emits and absorbs radiations of all frequencies, is called a black body and the radiation emitted by such a body is called
(a) black body radiation
(b) None of these
(c) white body radiation
(d) black body emission

Answer: A

Question. Which one of the following is not the characteristic of Planck’s quantum theory of radiation ?
(a) The energy is not absorbed or emitted in whole number or multiple of quantum
(b) Radiation is associated with energy
(c) Radiation energy is not emitted or absorbed continuously but in the form of small packets called quanta
(d) This magnitude of energy associated with a quantum is proportional to the frequency.

Answer: A

Question. The value of Planck's constant is 6.63 × 10^–34 Js. The velocity of light is 3.0 × 108 m s^–1. Which value is closest to the wavelength in nanometers of a quantum of light with frequency of 8 × 10¹⁵ s^–1 ?
(a) 4 × 10¹
(b) 2 × 10^–25
(c) 3 × 10⁷
(d) 5 × 10^–18

Answer: A

Question. In the photo-electron emission, the energy of the emitted electron is
(a) smaller than the incident photon
(b) same as than of the incident photon
(c) greater than the incident photon
(d) proportional to the intensity of incident photon

Answer: A

Question. When a metal surface is exposed to solar radiations
(a) The emitted electrons have energy less than a maximum value of energy depending upon frequency of incident radiations
(b) The emitted electrons have energy less than maximum value of energy depending upon intensity of incident radiation
(c) The emitted electrons have zero energy
(d) The emitted electrons have energy equal to energy of photons of incident light

Answer: A

Question. In continous spectrum light of _(i_)_ wavelength is deviated the _ii_
(a) (i) = longest, least
(b) (i) = shortest, most
(c) (ii) = shortest, least
(d) (i) = longest, most

Answer: A

Question. Which of the following statements do not form a part of Bohr’s model of hydrogen atom ?
(a) The position and velocity of the electrons in the orbit cannot be determined simultaneously
(b) Electrons revolve in different orbits around the nucleus
(c) The electron(s) in the orbit nearest to the nucleus has the lowest energy
(d) Energy of the electrons in the orbits are quantized

Answer: A

Question. An electron from one Bohr stationary orbit can go to next higher orbit
(a) by absorption of electromagnetic radiation of particular frequency
(b) by absorption of any electromagnetic radiation
(c) by emission of electromagnetic radiation
(d) None of these

Answer: A

Question. In Bohr’s model, atomic radius of the first orbit is y, the radius of the 3rd orbit, is
(a) 9y
(b) y
(c) y / 3
(d) 3y

Answer: A

Question. The radius of 1st Bohr’s orbit for hydrogen atom is ‘r’. The radius of second Bohr’s orbit is
(a) 4r
(b) 4r²
(c) r³
(d) None of these

Answer: A

Question. The third line of the Balmer series, in the emission spectrum of the hydrogen atom, is due to the transition from the
(a) fifth Bohr orbit to the second Bohr orbit
(b) fourth Bohr orbit to the first Bohr orbit
(c) sixth Bohr orbit to the third Bohr orbit
(d) seventh Bohr orbit to the third Bohr orbit

Answer: A

Question. Which one of the following pairs is not correctly matched ?
(a) Bohr-Isotopes
(b) J.H. Chadwick-Neutron
(c) J.J. Thomson-Electron
(d) Rutherford-Proton

Answer: A

Question. If r is the radius of the first orbit, the radius of nth orbit of H-atom is given by
(a) rn²
(b) rn
(c) r² n²
(d) None of these

Answer: A

Question. The radius of hydrogen atom in the ground state is 0.53 Å. The radius of Li²⁺ ion (atomic number = 3) in a similar state is
(a) 0.17 Å
(b) 0.53 Å
(c) 0.265 Å
(d) 1.06 Å

Answer: A

Question. In a hydrogen atom, if energy of an electron in ground state is 13.6. eV, then that in the 2nd excited state is
(a) 1.51 eV
(b) 6.04 eV
(c) 3.4 eV
(d) 13.6 eV.

Answer: A

Question. The energy of an electron in second Bohr orbit of hydrogen atom is
(a) –5.44 × 10^–19J
(b) –5.44 × 10^–19cal
(c) –5.44 × 10^–19eV
(d) –5.44 × 10^–19kJ

Answer: A

Question. The ionisation potential of a hydrogen atom is –13.6 eV. What will be the energy of the atom corresponding to n = 2.
(a) – 3.4 eV
(b) – 1.7 eV
(c) – 6.8 eV
(d) –2.7 eV

Answer: A

Question. The line spectrum of He⁺ ion will resemble that of
(a) hydrogen atom
(b) helium atom
(c) Li⁺ ion
(d) lithium atom

Answer: A

Question. What does negative sign in the electronic energy for hydrogen atom convey.
(a) The energy of electron in the atom is lower than the energy of a free electron of rest
(b) The energy of electron in the atom is lower than the energy of a free electron in motion
(c) The energy of electron decreases as it moves away from nucleus
(d) Energy of electron

Answer: A

Question. In which of the following Bohr’s stationary state, the electron will be at maximum distance from the nucleus ?
(a) Vth
(b) IInd
(c) Ist
(d) IIIrd

Answer: A

Question. The wavelength of the radiation emitted, when in a hydrogen atom electron falls from infinity to stationary state 1, would be (Rydberg constant = 1.097×10⁷ m^–1)
(a) 91 nm
(b) 406 nm
(c) 192 nm
(d) 9.1×10^–8 nm

Answer: A

Question. According to the Bohr theory, which of the following transitions in the hydrogen atom will give rise to the least energetic photon ?
(a) n = 6 to n = 5
(b) n = 6 to n = 1
(c) n = 5 to n = 4
(d) n = 5 to n = 3

Answer: A

Question. The shortest wavelength in hydrogen spectrum of Lyman series when R_H = 109678 cm^–1 is
(a) 911.7Å
(b) 1215.67Å
(c) 1002.7Å
(d) 1127.30Å

Answer: A

Question. Bohr model can explain
(a) spectrum of any atom or ion containing one electron only
(b) the spectrum of hydrogen atom only
(c) the spectrum of hydrogen molecule
(d) the solar spectrum

Answer: A

Question. Which of the following statements do not form a part of Bohr’s model of hydrogen atom ?
(a) The position and velocity of the electrons in the orbit cannot be determined simultaneously
(b) Electrons revolve in different orbits around the nucleus
(c) The electron in the orbit nearest the nucleus has the lowest energy
(d) Energy of the electrons in the orbits are quantized

Answer: A

Question. Bohr’s model is not able to account for which of the following.
(a) Spectrum of neutral helium atom.
(b) Stability of atom
(c) Energy of free electron at rest
(d) Calculation of radii of the stationary states

Answer: A

Question. If electron, hydrogen, helium and neon nuclei are all moving with the velocity of light, then the wavelength associated with these particles are in the order
(a) Electron > hydrogen > helium > neon
(b) Electron > helium > hydrogen > neon
(c) Electron < hydrogen < helium < neon
(d) Neon < hydrogen < helium < electron

Answer: A

Question. The de Broglie wavelength of a tennis ball of mass 60 g moving with a velocity of 10 metres per second is approximately
(a) 10^–33 metres
(b) 10^–16 metres
(c) 10^–31 metres
(d) 10^–25 metres

Answer: A

Question. If the energy difference between the ground state of an atom and its excited state is 4.4 × 10^–4 J, the wavelength of photon required to produce the transition
(a) 4.52 × 10^–12 m
(b) 1.13 × 10^–12 m
(c) 2.26 × 10^–12 m
(d) 4.52 × 10^–16 m

Answer: A