SHARMA CLASSES BHARATPUR

  Need for the Periodic Classification of Elements:- When there were only 31 elements it was relatively easy to study the properties of these chemical elements individually. Due to discovery of new elements it is difficult to study the properties of every element individual and making it difficult to remember the behavior and properties of these elements. This created the need for the periodic classification of elements. Advantages of classification:     Classification of elements provides as a fixed pattern in which the element change their properties.    It is also make easy to understand how similar elements form the compounds and so predict the compound formation.    Helps in discovering new elements 1.      Lavoisier's Classification (1789) - 33 elements Lavoisier's classification was based on the basis of the physical properties of the elements, such as hardness, malleability and lustre. He classified the elements into...

  Evolution:  It is the sequence, of gradual, irreversible changes which took place in the primitive organisms over millions of years to form new present-day species. Variations that resulted in formation of new species occurred basically due to errors in DNA copying as well as due to sexual reproduction. An Illustration to show variations in a population: A group of twelve red beetles live in green bushes and reproduce sexually so are likely to develop variations. There are the following possibilities First situation:  Crows eat these beetles as they can easily pick up red ones in the green bushes There is a colour variation during sexual reproduction and green beetles appears, it reproduces and its population increases. Crows are not able to see green beetles so their population continues to increase but that of red beetles decreases. This type of variation gives a survival advantage. Second situation:  Due to a colour variation few blue beetle appear forming...