Moseley established a more accurate periodic table by closer determination of atomic numbers. Through the results of his measurements of the wavelengths of the X-ray spectral lines of a number of elements which showed that the ordering of the elements by atomic number.
Answer:
Because: The mixtures contain unwanted substances which may be harmful and may degrade the properties of mixtures. So we, need to separated them and extract useful substances.
Answer:
Stars which never disappear below the horizon are called <u>circumpolar</u> stars.
