Jun 282013
 

Modern houses have different types of necessities for being satisfactory and easy to live. Among them, septic tanks are also the one. Septic tanks are the tanks in which all the biological waste materials like faeces, urines etc. produced by a house are stored. They help in decreasing the pollution that is taking place in the water sources these days. By the use of septic tanks, there won’t be need to directly dispose our waste products to water sources like rivers, lakes, ponds etc.

Since this is the era of development and information technology, there is a rapid use of Internet in this field too. There are different websites in the Internet which can provide the services of cleaning septic tanks. If you are staying in Hollywood, you can visit the link given so as to get help in septic tank cleaning hollywood. By clicking on the link, you can get more information about this website and its services. Thank you for reading this post!

Jun 272013
 

Chemistry is a vast subject. This is the branch of science that deals with the study of different chemicals, elements, compounds etc. We can find huge number of laws, theories and hypothesis in this subject. Some of them are Dalton’s Atomic Theory, Hund’s rule, Aufbau Principle etc. Among them, VSEPR theory is also the one. This is the theory which was brought out by Sidwick and Powell in order to predict the shapes of the molecules theoretically. The full form of VSEPR is Valence Shell Electron Pair Repulsion.

This theory is based on the fact that electron pairs in valence shell of an atom try to remain as far apart as possible so as to have minimum repulsion between them and the molecules take the shape on the basis of the number and nature of electron pair in the valence shell. The basic assumptions of VSEPR theory are:

  • A covalent molecule consists of a central atom to which other atoms are attached.
  • The valence shell of central atom consists of electrons in pair which may be bond pair or lone pair.
  • The repulsion between the electron pairs decreases in the order given below:
    lone pair-lone pair > lone pair-bond pair > bond pair-bond pair
  • The molecules take the shape so that there is minimum repulsion between the electron pairs.
  • The molecules with the central atom containing only the bond pairs in the valence shell have regular geometry while the molecules with the central atom containing the lone pairs will have irregular or distorted shape.