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Structure of the Atom

Timeline on Atomic Theory

     When scientists started exploring matter, they discovered that the smallest particle of an element that maintains its chemical identity through all chemical and physical changes is called and 'atom'.

Electrons and its Characteristics

     Although Dalton's theory of the existence of atoms was published in 1808, there was no clear idea of what an atom might look like until the early part of the twentieth century.

Models of Chemistry

     Scientific investigation on the structure of atom and its subatomic particles is an area where still absorbs scientists.


     The nuclei of atoms are made up of protons and neutrons. These two components of the nucleus are referred to as nucleons.

Arrangement of Electrons in an Atom (Bohr-Bury Scheme)

     Electrons revolve around the nucleus in different energy levels or shells and each shell is associated with definite energy.

Basics of Valency

     The outermost shell of an atom is called its Valence shell. It is the decisive shell during a chemical reaction.

Mass Number and Isotopes

     It is interesting to note that atoms of a given atomic number can have different number of neutrons.


     The nucleus contains protons and neutrons collectively called nucleons. It is positively charged. The mass of an atom is concentrated in the nucleus.

Question and Answers

Question and Answers 1

Question and Answers 2

Multiple Choice Questions


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