Table of Contents

Discovery of Proton

In 1886, E. Goldstein used perforated cathode in the immersion tube and observed new type of rays at low pressure
and high voltage, which were termed as positive rays. They are also known as the anode rays.

Properties of the Positive rays :

Positive rays move in a straight line.
Their charge to mass ratio (charge/mass i.e. e/m) depends on the nature of gas present in the tube.
They are affected by the electric and magnetic fields.
They are made up of positively charged particles.
They also are matter rays.

In 1919 this positive particle was identified as the proton and it was stated that in the atom the positively charged protons are also present along with the electrons. The atom is neutral because the number and charge of both is equal. The mass of proton is 1837 times greater than that of the electron.

The basic particles of atom are electron, proton and neutron.
The negatively charged particles in the atom are electrons.
The numeric value of the charge on electron and proton is the same but their sign is opposite.
James Chadwick discovered neutrons.
There are 6.022×10²³ particles in one mole. This is known as the Avogadro number.
The NTP volume of 1 mole of a gas is 22.4 litres.
The formula to determine the maximum number of electrons in a shell is 2n² .
When the atomic number is the same but mass number is different they are known as Isotopes.
Isobars are elements having different atomic number and the same mass number.
There are three isotopes of hydrogen, Protium, Deutirium and Tritium.

1. The Plum Pudding Model of atom was given by:
(a) Neil Bohr
(b) Thomson
(c) Ernest Rutherford
(d) Goldstein

Answer⇒ { B}

2. The discoverer of neutron was :
(a) C.V. Raman
(b) Rutherford
(c) J.J. Thomson
(d) James Chadwick

Answer ⇒ { D}

3. The size of atom is :
(a) 10^-6 cm
(b) 10^-15 cm
(c) 10^-2 cm
(d) 10^-8 cm

Answer ⇒ {D }

4. The number of neutrons in the Deutirium Isotope of hydrogen is /are :
(a) one
(b) Two
(c) Three
(d) Not even one

Answer ⇒ {A }

Discovery of Proton ?