Question

explain discovery of electron,proton and neutron? for class 9 science​

Answer 1

Discovery of Electron:

By J. J. Thomson in 1897. He carried a cathode ray experiment in which observed a stream of negatively charged particles coming out of cathode towards the anode. These particles were named as electrons.

The discovery of the proton is credited to Ernest Rutherford, who proved that the nucleus of the hydrogen atom (i.e. a proton) is present in the nuclei of all other atoms in the year 1917. Based on the conclusions drawn from the gold-foil experiment, Rutherford is also credited with the discovery of the atomic nucleus.

After the discovery of electrons and protons,it was noticed that all mass of an atom cannot be accounted for on the basis of only protons and electrons. Then the neutrons were discovered. Chadwick in 1932 discovered another subatomic particle called neutron. Neutron is present inside the nucleus.

Answer 2

Answer:

Discovery of Protons

The discovery of protons dates back to the year 1815 when the English chemist William Prout suggested that all atoms are made up of hydrogen atoms (which he referred to as protyles). When canal rays (positively charged ions formed by gases) were discovered by the German physicist Eugen Goldstein in the year 1886, it was observed that the charge-to-mass ratio of the hydrogen ion was the highest among all gases. It was also observed that the hydrogen ion had the smallest size among all ionized gases.

The nucleus of the atom was discovered by Ernest Rutherford in the year 1911 in his famous gold foil experiment.

Who Discovered Protons?

The discovery of the proton is credited to Ernest Rutherford, who proved that the nucleus of the hydrogen atom (i.e. a proton) is present in the nuclei of all other atoms in the year 1917.

Based on the conclusions drawn from the gold-foil experiment, Rutherford is also credited with the discovery of the atomic nucleus.

How was the Proton Discovered?

• Ernest Rutherford observed that his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air.

• Ernest Rutherford observed that his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air.After investigating further, Rutherford found that these hydrogen nuclei were produced from the nitrogen atoms present in the atmosphere.

• Ernest Rutherford observed that his scintillation detectors detected hydrogen nuclei when a beam of alpha particles was shot into the air.After investigating further, Rutherford found that these hydrogen nuclei were produced from the nitrogen atoms present in the atmosphere.He concluded that the hydrogen nuclei originated from the nitrogen atom, proving that the hydrogen nucleus was a part of all other atoms.

Discovery of Neutrons

The discovery of neutrons can be traced back to the year 1930 when the German nuclear physicists Herbert Becker and Walther Bothe observed that a penetrating form of radiation was produced when the alpha particles emitted by polonium was incident on relatively light elements such as lithium, beryllium, and boron.

The presence of neutral particles in the nuclei of atoms was also suggested by Ernest Rutherford in the year 1920. He suggested that a neutrally charged particle, consisting of a proton and an electron bound to each other, also resided in the nuclei of atoms. He coined the term ‘neutron’ to refer to these neutrally charged particles.

Who Discovered Neutrons?

The British physicist Sir James Chadwick discovered neutrons in the year 1932. He was awarded the Nobel Prize in Physics in the year 1935 for this discovery.

It is important to note that the neutron was first theorized by Ernest Rutherford in the year 1920.

How were Neutrons Discovered?

• James Chadwick fired alpha radiation at beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation.

• James Chadwick fired alpha radiation at beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation.This radiation was made incident on paraffin wax, a hydrocarbon having a relatively high hydrogen content.

• James Chadwick fired alpha radiation at beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation.This radiation was made incident on paraffin wax, a hydrocarbon having a relatively high hydrogen content.The protons ejected from the paraffin wax (when struck by the uncharged radiation) were observed with the help of an ionization chamber.

• James Chadwick fired alpha radiation at beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation.This radiation was made incident on paraffin wax, a hydrocarbon having a relatively high hydrogen content.The protons ejected from the paraffin wax (when struck by the uncharged radiation) were observed with the help of an ionization chamber.The range of the liberated protons was measured and the interaction between the uncharged radiation and the atoms of several gases was studied by Chadwick.

• James Chadwick fired alpha radiation at beryllium sheet from a polonium source. This led to the production of an uncharged, penetrating radiation.This radiation was made incident on paraffin wax, a hydrocarbon having a relatively high hydrogen content.The protons ejected from the paraffin wax (when struck by the uncharged radiation) were observed with the help of an ionization chamber.The range of the liberated protons was measured and the interaction between the uncharged radiation and the atoms of several gases was studied by Chadwick.He concluded that the unusually penetrating radiation consisted of uncharged particles having (approximately) the same mass as a proton. These particles were later termed ‘neutrons’.