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Atomic Structure

Dalton's atomic theory proposed a simple description of matter as composed of atoms. According to the Bohr, negatively charged particle are revolving around the nucleus in a fixed orbit known as electrons and the center part called nucleus is consists of neutrons and protons. Protons have positive charge and neutrons are charge less particle. Since the electrons are revolving around the fixed orbit, there is no loss of energy. Loss or gain of energy takes place when electron jumps from one orbit to the other orbit.

Rutherford's experiment on the scattering of alpha particles led Bohr to the theory of Atomic structure that the atom consists of a positively charged nucleus at its center. His theory is mainly based on the following postulates.

  • An atom consists of a positively charged nucleus at the center.
  • The negatively charged particles known as electrons move around the nucleus in various orbits known as stationary energy levels. The electrons cannot emit radiations when moving in their own stationary levels. 
  • The Coulombarian and Newtonian forces are applicable in the domain of the atom.
  • The electrons revolve around the nucleus in various circular orbits
  • When an electron jumps from a higher energy level to a lower energy level, it gives out electromagnetic radiations of a particular frequency. 


Related Calculators
Atomic Mass Calculator Grams to Atoms Calculator
 

Properties of Atom

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A simple definition of the atom is that it is the smallest particle that contains the properties of that element. Atoms having the following properties;
  • All elements are made up of indivisible, tiny particles known as atom.
  • For a same element, atoms are identical. The atoms are different for different elements.
  • Atoms of various elements can combine with any another in a simple whole number ratios to produce compounds.
  • Chemical reactions occur when atoms are joined separated or rearranged. 
  • Due to any chemical reaction, the composition of atoms cannot be changed.  

Physical Changes

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Physical changes alter only the physical properties of matter. No new substances are formed in a physical change. A physical change occurs when there is a change in the size, shape or appearance of a substance and when no chemical reaction has taken place. To change the phase or form of a material is to cause a physical change. Physical changes also occur when material is heated and expands. When a piece of metal is heated until it emits light, it has undergone a physical change. Most physical changes are easy to recognize because the observable properties of a substance change.

Chemical Changes

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Chemical changes cause changes in the chemical properties of matter. Chemical reactions can be classified as composition, decomposition, or displacement reactions. Chemical reactions produce changes in the chemical properties of the reacting matter to form new substances. All chemical reactions involve the exchange of energy. Many of the common changes in the world around us are chemical changes, examples being the rusting of iron, the tarnishing of silverware and the digestion of food. All chemical changes are either composition, decomposition or displacement reactions. 

More topics in Atomic Structure
Mechanical Properties of Matter
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