Model Of An Atom - Free MCQ Practice Test with solutions, Class 9

Sir James Chadwick, 20 October 1891 – 24 July 1974 was a British physicist who was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932.

When we rub a glass rod with a silk cloth, the glass rod gets charged. This charge produced on the rod comes from the atoms and charged particles present in the rod.

The proton has a charge equal in magnitude but opposite in sign to that of electron.

A proton has one unit positive charge whereas electron has one unit negative charge.

An anode ray (also positive ray or canal ray) is a beam of positive ions that is created by certain types of gas-discharge tubes. They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886.

Eugen Goldstein

They were first observed in Crookes tubes during experiments by the German scientist Eugen Goldstein, in 1886. Later work on anode rays by Wilhelm Wien and J. J. Thomson led to the development of mass spectrometry.

There is only one stable atom that does not have neutrons. It is an isotope of the element hydrogen called protium. Protium, which contains a single proton and a single electron, is the simplest atom. All other stable atoms contain some number of neutrons.

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.
Correct answer is C.

An electron is a negatively charged particle, whereas a proton is a positively charged particle. The magnitude of their charges is equal. Therefore, an atom containing one electron and one proton will not carry any charge.

Electron and proton were embedded in nucleus as said in watermelon experiment.

Canal rays are positively charged radiations which led to the discovery of another sub-atomic particle called protons.

J. J. Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. In Thomson's model, the atom is composed of electrons (which Thomson still called “corpuscles,” though G. J.

Subatomic particles include electrons, the negatively charged, almost massless particles that nevertheless account for most of the size of the atom, and they include the heavier building blocks of the small but very dense nucleus of the atom, the positively charged protons and the electrically neutral neutrons.

Thomson proposed the model of an atom to be similar to that of a Christmas pudding. The electrons, in a sphere of positive charge, were like currants (dry fruits) in a spherical Christmas pudding.

The essential conditions for the production of anode rays is high voltage and very low pressure in a discharge tube.

Here it means that when we compare the mass of protons and electrons. Electrons weigh much less than protons and therefore when the mass of an atom is calculated then just the mass of protons and neutrons is taken into consideration.