Author: Heba Soffar

Modern periodic Table 0

The attempts of the elements classification

The elements The scientists classified the elements according to their properties to facilitate their study and to find a relationship between the elements ,  and their chemical and physical properties .

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The types of the sound waves

The Sound waves There are two types of the sound waves which are the audible sounds and the non – audible sounds , The audible sounds such as the sonic waves , And the...