Test: Discovery Of Sub - Atomic Particles

15 Questions MCQ Test Chemistry For JEE | Test: Discovery Of Sub - Atomic Particles

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Which of the following statements is not correct about the characteristics of cathode rays?


Characteristics of cathode rays are:

(i) The cathode rays start from cathode and move towards the anode.

(ii) These rays themselves are not visible but their behaviour can be observed with the help of phosphor materials such as ZnS.

(iii) In the absence of electrical or magnetic field, these rays travel in straight lines.

(iv) In the presence of electrical or magnetic field, the behaviour of cathode rays are similar to that expected from negatively charged particles, suggesting that the cathode rays consist of negatively charged particles, called electrons.

(v) The characteristics of cathode rays (electrons) do not depend upon the material of electrodes and the nature of the gas present in the cathode ray tube.


The number of radial nodes for 3p orbital is __________.


Number of radial nodes = n - 1 – 1
For 3p orbital, n = 3 – 1 – 1 = 1
Number of radial nodes = 3 – 1 – 1 = 1. 


Principle Quantum number describes?


The principal quantum number (n) describes the size of the orbital. Orbitals for which n = 2 are larger than those for which n = 1, for example. Because they have opposite electrical charges, electrons are attracted to the nucleus of the atom.

Energy must therefore be absorbed to excite an electron from an orbital in which the electron is close to the nucleus (n = 1) into an orbital in which it is further from the nucleus (n = 2). The principal quantum number therefore indirectly describes the energy of an orbital.


The atoms of different isotopes of same element differ from each other in the number of


Isotopes of an element will contain the same number of protons and electrons but will differ in the number of neutrons they contain. In other words, isotopes have the same atomic  number because they are the same element but have a different atomic mass because they contain a different number of neutrons.


An element has 18 electrons, and 20. neutrons. Its charge is -2. What is its mass number?


Mass no.= no. of proton + no. of neutron

Here no. of proton is 2 less than no. of electron as the charge on element is -2

Hence no. of proton = 18 - 2 = 16,

No. of neutron = 20

Hence mass number is 16 + 20 = 36


The radius of the nucleus of an atom is approximately:


The proton distribution can be characterized by an average radius. It is found that nuclear radii range from (1-10) x 10-15 m.


Thomson’s plum pudding model explained:


Postulates of Thomson’s atomic model

  • An atom consists of a positively charged sphere with electrons filled into it. The negative and positive charge present inside an atom are equal and as a whole, an atom is electrically neutral.
  • Thomson’s model of the atom was compared to plum pudding and watermelon. He compared the red edible part of the watermelon to positively charged sphere whereas the seeds of watermelon to negatively charged particles.

Which of the following conclusions could not be derived from Rutherford’s α -particle scattering experiment?


Concept of electrons moving in a circular path of fixed energy called orbits was put forward by Bohr and not derived from Rutherford's scattering experiment.

Out of a large number of circular orbits theoretically possible around the nucleus. The electron revolves only in those orbits which have a tired value of energy Hence, these orbits are called energy level or stationary states.


Which model describes that there is no change in the energy of electrons as long as they keep revolving in the same energy level and atoms remains stable?


The given carbohydrate is α – D – (-) – Fructofuranose. This is because the -OH group is present on the right hand side.


Atomic mass of an element is equal to the sum of?


Atomic Mass is the sum of no. of protons and neutrons.


The charge on electron was determined by


The charge on electron was determined by milliken by using oil drop experiment


The nature of positive rays depends on?


The positive charges in these rays, other than negative cathode rays (which are electrons), depend on the gas that is used because they are cations - atoms with mostly one electron missing and thus one positive charge. So, if you accelerate, argon cations and protons over the same electric potential, the particles in the rays will have the same kinetic energy, but the argon ions will be much slower, as they are much heavier than the protons.


The nucleus of a tritium atom, 3H, contains


Tritium (3H) is a radioactive isotope of hydrogen. The nucleus decays (by emittingan electron and an antineutrino), changing from a triton (one proton and two neutrons) to a 3He nucleus (two protons and one neutron).


Which of the following is true about electron:


Electron carries unit negative charge and has a mass of 9.1 x 10-31 kg, while proton has a mass of 1.67 x 10-27 kg


Neutron is a fundamental particle which carries?


A neutron is a sub-atomic particle with no net electrostatic charge, with a very similar mass to a proton.