NEB Notes for All Nepali Students!

VALENCE SHELL ELECTRON PAIR REPULSION THEORY (VSEPR Theory) :                                                                             VSEPR theory is based on the idea that electron pairs try to be far apart as possible in the central atom of a covalent molecule. The shape of molecules depends on the number and nature of electron pairs present in the valence shell of central atom of molecule.  Postulates/Assumptions of VSEPR theory : 1.) In a covalent molecule or an ion, there is a central atom to which all other atoms are attached. 2.) Pair of electrons are present in the valence shell of central atom. They are of following types :      a.) Bond pair : The pairs taking part in the reaction.      b.) Lone pair : The pairs left out during bon...

MAGNET :                                             A magnet is a material which has its atoms arranged in such a way that it exhibits attractive and directive characters. Properties of Magnet : 1.) A magnet has attractive property . It can attract ferromagnetic materials like iron, nickel, cobalt and their alloys. The strength of attraction follows the inverse square law. Ferromagnetic materials : The substances like iron, below a certain temperature (curie point) can possess magnetization (magnetic property) in the absence of an external magnetic field.  These substances are called ferromagnetic materials.  2.) A magnet's strength is concentrated in two poles i.e. North pole and South Pole . NOTE:             Even if we break/cut a magnet, the broken pieces will also have both the poles. A magnet having only a single pole ...