Everything around us is made up of tiny particles of matter called atoms. Two or more atoms of the same or different type forms the molecules, which is the basis of each substance. For example: - a water molecule has two atoms of hydrogen and one atom of oxygen.

Molecules of solid substances are bound together with a force which is very strong. The force which binds molecules of liquid is much weaker, and molecules in gases move in every direction. Atoms are made up of much smaller particles called protons, neutrons and electrons. Protons and electrons have an electrical charge.
Protons and neutrons are heavier than electrons and reside in the centre of the atom, which is called the nucleus. Electrons have a negative charge and move around the nucleus. Protons have a positive charge and are tied to the nucleus. Neutrons are uncharged particles.


The number of protons in the nucleus defines to what chemical element the atom belongs. The number of protons in an atom is referred to as the atomic number of that element. The Periodic Table of the Elements arranges elements in order of increasing atomic number.
The carbon atoms have six protons, hydrogen atoms have one and oxygen atoms have eight and are positioned accordingly on the periodic table.


Electrons surround the atomic nucleus in pathways called orbital. An atom's electron configuration is the orbital description of the locations of the electrons. Using the electron configuration and principles of physics, scientists can predict an atom's properties, such as stability, boiling point and conductivity.
For example, the electron configuration for Sodium (Na) is 1s22s22p63s1, but it's is written [Ne]3s1. [Ne] is equivalent to all the electron orbits in a Neon atom. The Letters, s, p, d, and f designate the shape of the orbitals and the superscript gives the number of electrons in that orbital.


The nucleus consists of Z protons, where Z is called the atomic number, and N neutrons, where N is the neutron number. The neutron number determines the isotope or nuclide. The atomic mass number, symbol A, equals Z+N.
For example, carbon has atomic number 6, and its abundant carbon-12 isotope has 6 neutrons, whereas its rare carbon-13 isotope has 7 neutrons. Some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes. Neutrons are required for the stability of nuclei.
Neutrons are produced copiously in nuclear fission and fusion. They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes. The neutron is essential to the production of nuclear power.

Fission and fusion are nuclear reactions that produce energy. They both have different applications.

Fission is the splitting of a heavy, unstable nucleus into two lighter nuclei. Nuclear fission requires extremely highly temperatures and releases a large amount of energy. /images/technology/nuclear_fission.png

Fusion is the process where two light nuclei combine together releasing vast amounts of energy. It is a controlled chain reaction. /images/technology/nuclear_fusion.jpg

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