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Atoms And Nuclei Physics Class 12 Notes
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An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element. Every solid, liquid,gas and plasma is composed of neutral or ionizedatoms atoms are extremely small ; typical sizes are around 100 picometers.
( ten – billionth of a meter, in the short sacale )..

Atoms are small enough that attempting to predict their behavior using classical physic, as if they were billiard balls, for example, gives noticeably incorrect prediction due to quantam effect through the development of physic, atomic models have incorporated quantam principles to better explain and predict this behaviors.

Every atoms is composed of a nucleus and one or more electrons bound to the nucleus..

The nucleus is made of one or more protons and typically a simar number of neutrons. Protons and nucleus. The protons have a positive electric charge, and the electrons have a negative electric charge.if the number of proton and electron are equal that atoms is electrically neutral.

If an atom has more or fewer electrons than protons, then it has an overall negative or positive charge respectively, and it is called an ion..


The atomic nucleus is the small,dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiget -Marsden gold foil Experiment.

After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri lvanenko and Werner Heisenberg an atom is composed of a positively charged nucleus,with a cloud of negatively charged electron surrounding it bound togather by electrostatic force..

Almost all of the masd of ab atom is located in the nucleus,witb a very small contribution from the electrons cloid. Proton and neutrons are bound togather to from a nucleus by the nuclear force..

The diameter of the nucleus is in the range of 1.7566 fm.(1.7566×10-15 m ) for hydrogen to about 11.714 fm for the heaviest are much smaller than the diameter of the atom itself ( Nucleus + Electrons Cloud ) by a factor of about 26,634 (Uranium atomic radius is about 156 pm) to about 60,250 ( hydrogen atomic redius is about 52.92pm )

The branch of physics concerned with the study and understanding of the atomic nucleus, including its composition and the force which bind it togather, is called nuclear physics..


Book Name : Atoms and Nuclei
Size : 700KB
Number Of Page : 10



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