The mass of a neutron is almost the same as that of a proton i.e. The total number of protons in the atoms of an element is always equal to the atomic number of the element. Protons are over 1800 times heavier than electrons. The mass of a proton is approximately 1.672 × 10 -24 The charge of a proton is 1e, which corresponds to approximately 1.602 × 10 -19 Protons are positively charged subatomic particles. He cannot explain the line spectrum / discrete spectrum of atoms. So, Rutherford cannot explain the stability of atoms. So according to this electron will collide with the nucleus and the atom will destroy. Maxwell Theory: Any accelerated charge particle emits radiation and loses energy. Number of protons is the same as the number of electrons.Įlectrons revolve around the nucleus in a closed circular orbit. Positive charge resides in very small space i.e nucleus. Positive charges are heavy charges known as nucleus. Very few i.e 1 out of 2000 returns back i.e deflected at 180 degree. Some of the alpha particles were deflected by small angels. Nearly 99.9% of the alpha particle passed undeviated. Observation of Alpha Scattering Experiment The ZnS screen is placed behind the gold foil. Construction of Alpha Scattering ExperimentĪ very thin gold foil of 1000 atoms thick is taken.Īlpha rays (doubly charged Helium He 2 + ) were made to bombard the gold foil. It is also known as the alpha scattering experiment. Also properties of cathode rays remain unchanged. On changing the gas and electrode rod material. They are deflected towards the positive charged plate in the electric field.

A small amount of energy is transformed into X-rays. When the electrons hit the far end of the tube they give up all the energy they carry due to their speed and this is changed to other forms such as heat. As, electrons are accelerated from one end of the tube to the other using an electric field.

When an electron beam is deflected then the image is on the projector. It was invented in 1897 by the german physicist Karl Ferdinand. In case they gain energy they jump to a higher energy level and if they lose energy then they jump to a lower energy level.Īmount of energy gain or loss is equal to the difference in two energy levels.Ī cathode-ray tube (CRT) is a vacuum tube in which an electron beam, deflected by applied electric or magnetic fields, produces a trace on a fluorescent screen. Other scientists discovered that electrons can gain energy or lose energy. It is applicable only for hydrogen and hydrogen-like atoms. While revolution, electrons neither gain nor lose energy. It tells us about different atomic particles.Ītom is made up of positive charge and electrons are embedded like plum pudding or watermelon model.Įlectrons revolve around the nucleus in a fixed orbit with fixed energy and fixed velocity.Įlectrons revolve only in those angular momentum which is integral multiple of nh/2 pi.ĭuring revolution there is electrostatic force between the nucleus and electron which gives centripetal force. Particles of atoms are divisible which was proved later. There is no well defined definition of the structure of an atom. This theory was not able to explain the existence of isotopes. The Atoms of different elements are different.Įvery matter is made up of a fundamental unit known as matter.Ītoms of different elements are different.Įach atom has its specific mass which varies from atom to atom.Ītoms undergo rearrangement during a chemical reaction. Smallest fundamental particle is atom and atom can not be further subdivided. The first scientific theory of atomic structure was proposed by John Dalton in the 1800s. There are so many assumptions regarding the model of atoms and there are so many discovered models on atomic structure. While revolution there is neither gain nor loss of energy. While revolving around the nucleus electrostatic field is present between the nucleus and electron which provides centripetal force also. It also has protons and the number of electrons are equal to the number of protons. Atomic structure consisting of a center called nucleus and electron revolve around the nucleus in a fixed circular orbit with fixed energy and fixed velocity.

John dalton atomic theory