I have given short descriptions about the Scientists related to atomic structure, some animated videos of atomic models, and little bit information on electronic configuration.

Structure of Atom(SCERT CLASS IX)

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JAMES CHADWICK(1891-1974)

In 1932, Chadwick proved scientifically that inside the nucleus of an atom, there are neutral particles having mass equal to that of protons. This charge-less particle is the Neutron. The total mass of an atom is concentrated in the nucleus because the particles protons and neutrons that posses mass are in the nucleus.

J J THOMSON(1856-1940)

J J Thomson modified the discharge tube experiments by scientists before him. He conducted cathode ray tube experiment and observed the cathode rays. He analysed them under different conditions and proved that the rays contained negatively charged particles with mass and energy, and these particles are identical irrespective of the gas filled in tube. So the particles are part of atom and known as Electrons. Thus, he established that atom is divisible

Atoms are basic unit of matter and defining structure of elements

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STRUCTURE OF ATOM

e-Book prepared by Rugma Nair B.Ed. Physical Science Peet Memorial Training College Mavelikkara

But there was a limitation to Rutherford's model. What may be that? Check the video..

CATHODE RAY TUBE EXPERIMENT

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SIR HUMPHREY DAVY(1778-1829)

Sir Humphrey Davy used electricity to isolate many elements like Na, K, Ca, Mg etc from their compounds. Through his experiments he inferred that electric charges are present in substances

ALPHA RAY SCATTERING EXPERIMENT

John Dalton(1766-1844)

John Dalton proposed the <a href="https://diksha.gov.in/play/collection/do_31277293977118310414749?contentId=do_31290189596922675211610">Atomic Theory</a> in 1807 for the study of atoms and for finding how matter has been formed. According to Dalton, matter is made up of indivisible atoms

MICHAEL FARADAY(1791-1867)

Michael Faraday is known as the father of electricity. He found that electricity can pass through liquids. it is found that some liquid substances can be separated into their components by passing electricity through them. But, he failed to explain the reason behind this process

RUTHERFORD'S PLANETARY MODEL OF ATOM

Rutherford proposed a model for atom similar to solar system, which was more or less acceptable model. He suggested that electrons are revolving around nucleus at the center, similar to planets revolving around Sun. Hence the name <a href="https://diksha.gov.in/play/collection/do_31277293977113395214743?contentId=do_31290189738605772811612">Planetary Model</a>.

Atoms of all elements are made up of the particles electron, proton and neutron. The difference in the number of these particles make an element different from that of others. Atoms are electrically neutral since number of electrons and protons in an atom are equal.

NIELS BOHR(1885-1962)

Overcoming the limitation of Rutherford's model, Bohr proposed a new and better atomic model. This model is known as <a href="https://diksha.gov.in/play/collection/do_31277293977125683214758?contentId=do_3129018991912714241245">Bohr's Model</a>. In this model, electrons revolve around the nucleus in some fixed paths, where energy is constant. The paths traced by electrons are called shells or orbits.

Haven't you seen some numbers above and below each elements in a periodic table. What are they? Let's go through the video..

ERNEST RUTHERFORD(1871-1937)

Even though Eugen Goldstein recognized the presence of positive charge in atoms in 1886, it was Rutherford who proved it authentically. Through his alpha ray scattering experiment, he substantiated that major portion of atom is empty and there is a small part inside the atom where all positive charge is concentrated. This central region is called Nucleus of the atom. The particles inside the nucleus which are positively charged are called Protons whose charge is equal and opposite to that of electrons.

ELECTRONIC CONFIGURATION OF AN ATOM

Filling up of electrons in the increasing order of energy levels is known as electronic configuration. This is based on the following principles

1. The maximum number of electrons that can be accomodated in any given shell is 2n^2(n=shell number) 2. Filling up of electrons in shells of higher energy happens only after the shells of lower energy are filled. 3. The maximum number of electrons that can be accomodated in the outermost shell of an atom is 8.

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