ATOMIC STRUCTURE,ATOMIC NUMBER,MASS NUMBER ETC

ATOMIC STRUCTURE - all the matter is composed of atoms. the atoms i very small and its diameter is of   1 × 10⁻¹⁰ meter. every atoms possesses a central core called nucleus, which is positive charged the diameter of the nucleus is of the order of  10⁻¹⁴ .the nucleus consists of two important particles called protons and neutrons.the protons are positive charged and neutron has no charged. the space around the nucleus consist of another important particles called electron. the electron are negatively charged particles and they revolve round the nucleus in elliptical orbit. no of electrons in an atom is equal to no of protons.

ATOMIC MODEL - To explain the nature of atom, many models have been proposed. they are Thomson model,niels-bohr model and sommer field model.

THOMSON MODEL - Now the problem was to understand the structure of the atom with these particles. Sir Thomson was the first to attempt to explain it. He said that the atom is like a round Christmas cake, in which the cake is made of positive charge (protons) and there is Meva Negative charge (Electron). We can also think of it as a watermelon in which the red part is positive and the seeds are negatively charged. The amount of positive and negative charge is the same, making the atom neutral. The weight of an atom is normally distributed throughout the circle.

RUTHERFORD MODEL - On the basis of this experiment, a scientist named "Rutherford" conducted another experiment, so that he could know the location of Electron. He took gold foil because he wanted a very thin layer. Then they rapidly fired alpha particles (helium atoms with no electron) on it. The alpha particle weighed 4u, so it had a lot of energy. He expected that according to the Thomson model, almost all the alpha particles would return to collide with the protons. But the results were shocking.

Almost all the alpha particles went through the gold foil.

A few particles bent slightly.

Only one particle returned 180 out of an estimated 12000.

BOHR MODEL - neil bohr suggested that the electrons are negatively charged particles and move around the nucleus in various orbits.the orbits of electron is fixed. he gave name energy levels to these orbits.the electron cannot emit any energy when it moves in its own fixed orbits known as stationary energy levels.

SOMMERFIELD MODEL - sommerfield postulate that some of the electron orbits are spherical while some other orbits are elliptical in shape. later it was proposed that each energy level have sub energy levels called sub shells,namely,p,d and f in the order of increasing energy.for particular value of n,there are equal no of possible sub-shells,out of which one is spherical and the remaining are elliptical in shape.the sub-shells are designated by the letter l known as orbital or azimuthal quantum numbers. for a particular value of n,the different value of l are 0,1,2,3........(n-1).

ATOMIC NUMBER - the atomic no of an atom is the no of protons in the nucleus which is equal to the no of electrons of the atom.it is denote by Z.

MASS NUMBER - The mass no of the atom is the total numbers of the protons and neutrons in the nucleus.it is denote by A.the mass no also refers to the atomic weight of the element and mass no of element always a whole number where atomic weight may be whole number or fraction.

ISOTOPES- the atoms composed of nuclei with same number of protons but different number of neutrons are called isotopes.in other words,isotopes have the same atomic number and different mass numbers.

ISOBARS - ISOBARS are the atoms of different elements which have same mass number but different atomic number.