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| Moving process of Atom |
Every single thing you can see, hear, feel, smell, and taste
is made from microscopic particles. These particles are called atoms, and it
would take millions of them just to cover a full-stop. An atom is itself made
up of even smaller particles. In the center of each atom there is a nucleus
made up of protons and neutrons. Particles called electrons whiz around this
nucleus in different shell(layers). Protons and neutrons are much heavier than
the electrons, so the nucleus makes up most of an atom’s mass. Some substances,
such as water, are made up of molecules. These consist of several kinds of atoms
joined together in a group. Other substances, such as iron, have just one kind
of atom.
Protons, Neutrons, & Electrons.
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| Proton, Neutron and Electron |
The nucleus of every atom contains two types of particle
protons and neutrons. The number of protons gives the atomic number. Protons have
a positive electric charge, while neutrons have none. The electrons that spin
around the nucleus, like planets orbiting the sun, have a negative charge. But
electrons are not solid balls, they are bundles of energy that move almost as
fast as light. There are always the same number of electrons and protons in an
atom.
Nucleus.
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| Nucleus |
A nucleus is made up of two types of particles, neutrons
which do not carry any charge; and protons which carry a positive charge
exactly equal in magnitude to that of an electron; i.e. 1.6 * 10-19
coulomb. Protons and neutrons have
similar masses, but neutron is slightly heavier; both of them being much more
massive than electrons. Neutron is 1838.65 times more massive than an electron,
proton is 1836.12 times more than electron. The simplest nucleus is that of an
atom of ordinary hydrogen and consists
of only a single proton. Both protons and neutrons are commonly known as
nucleons.
The Schrodinger Model :- abandoned the idea of precise orbits,
replacing them with a description of the regions of space ( called orbitals)
where the electrons were most likely to be found.
Orbitals:- electrons with various values of angular
momentum occupy regions of space like these. Shading sows probability of
finding an electron at that distance.
The Bohr Model :- ‘quantized’ the orbits in order to
explain the stability of the atom.
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| Bohr's Model |
The Rutherford Model :- pictured the atom as a
miniature solar system with the electrons moving like planets around the
nucleus.
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| The Rutherford Model |
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| Scattering experiment by Rutherford. |
Models of the Atom
Experimental data have been the impetus behind the creation
and dismissal of physical models of the atom. Rutherford’s model, in which
electrons move around a tightly packed, positively charged nucleus,
successfully explained the results of scattering experiments, but was unable to
explain discrete atomic emission—that is, why atoms emit only certain
wavelengths of light. Bohr began with Rutherford’s model, but then postulated
further that electrons can move only in certain quantized orbits; this model
was able to explain certain qualities of discrete emission for hydrogen, but
failed for other elements. Schrödinger’s model, in which an electron is
described not in terms of definite paths but in terms of the likelihood of
finding the electron in a particular region, can explain certain qualities of
emission spectra for all elements; however, further refinements of the model,
made throughout the 20th century, have been needed to explain further spectral
phenomena.
Nucleur fission
process.
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| Nucleur fission process |
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| Nucleur fission process |
When a nucleus is
bombarded with a neutron, it absorbs the neutron and then breaks up into two
roughly equal nuclei. This process is called the nuclear fission.
Nuclear Reactor activity.
A nuclear reactor works on the principle of steadily
sustained nuclear chain reaction. It uses fissile nuclei like 92u235 and Pu239 . Use
of appropriate moderator coolant and control rods are essential to the
proper design of a reactor using some specific fissile material as fuel gives
the scheme to a reactor using slow neutrons. The coolant flowing in
through X carries away the energy
generated in the form of heat through Y.
Fission and Fusion Processes.
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| Fission and Fusion Processes |
Nuclear energy can be released in two different ways: by fission
(splitting) of a heavy nucleus, or by fusion (combining) of two light nuclei.
In both cases energy is released because the products have a higher binding
energy than the reactants. Fusion reactions are difficult to maintain because
the nuclei repel each other, but, unlike fission reactions, fusion reactions
create far less radioactivity.
