Structure of an atom

Which of the following is responsible to rule out the existence of definite paths or trajectories of electrons?

• Pauli’s exclusion principle.

• Heisenberg’s uncertainty principle.

• Hund’s rule of maximum multiplicity.

• Aufbau principle.

Which of the following statements does not form a part of Bohr's model of hydrogen atom?

• Energy of the electrons in the orbit is quantised

• The electron in the orbit nearest the nucleus has the lowest energy

• Electrons revolve in different orbits around the nucleus

• The position and velocity of the electrons in the orbit cannot be determined simultaneously

Balmer series appear in the

• IR region

• X-Ray region

• Visible region

• UV region

The spectra which is also known as the line spectra is

• Spectrosocopy

• absorption spectra

• emission spectra

• continuous spectra

Millikan's oil drop experiment determined the

• Mass of proton

• Presence of neutron

• Charge of electron

• Size of electron

Wave number is defined as

• the number of wavelengths per unit length

• the number of frequencies per unit length

• reciprocal of wavelength

• all of the above

Which of the following is not a postulate of Bohr's model

• The electron in the hydrogen atom can move around the nucleus in a circular path of fixed radius and energy.

• The angular momentum of an electron is quantised.

• The energy of an electron in the orbit does not change with time.

• The energy change takes place in a continuous manner

Which of the following conclusions could not be derived from Rutherford’s

α -particle scattering experiment?

• Most of the space in the atom is empty.

• The radius of the atom is about 10^–10 m while that of a nucleus is 10^–15 m.

• Electrons move in a circular path of fixed energy called orbits.

• Electrons and the nucleus are held together by electrostatic forces of attraction.

Which of the following statement is not correct about the characteristics of

cathode rays?

• They start from the cathode and move towards the anode.

• They travel in a straight line in the absence of an external electrical or magnetic field.

• Characteristics of cathode rays do not depend upon the material of electrodes in a cathode ray tube.

• Characteristics of cathode rays depend upon the nature of gas present in the cathode ray tube.

Which of the following statements about the electron is incorrect?

• It is a negatively charged particle.

• The mass of an electron is equal to the mass of a neutron.

• It is a basic constituent of all atoms.

• It is a constituent of cathode rays.