CHEMISTRY WORLD

      In earlier 19th century about 30 elements were known and were classified in 3 types as metals, non metals and metalloids. In 1869 Russian chemist Dimitri Mendeleev put 4th periodic table of 63 elements using atomic mass and properties of elements. Meldeleev arranged the elements known at the time in an increasing order of their atomic masses. The orbital number of an element is called its atomic number.     Mendeleev's periodic table was revised in accordance with modern periodic law and called it modern periodic table . Mendeleev's periodic table is based on atomic mass of an element, modern periodic table is based on Atomic Number of element. Atomic number is related to number of electrons and number of electrons are changed in any reaction. Also chemical properties of atom depends on number of electrons. Hence modern periodic table based on Atomic number.      There are total 7 horizontal rows and 18 vertical coloumns named as periods a...

           Every thing around you is matter. you, your mother, your toys, everything is made up of matter. MATTER is anything that has mass and volume. It can be a pure substance or a mixture. Matter means everything around you is composed of atoms and molecules. So basically CHEMISTRY is how different atoms and molecules interact via chemical bonds to form new substances. Another question is Why chemistry is so important to us?     When you wake up in the morning, you start your day with toothpaste- a chemical compound. After that you take a bath for which you use a soap -a chemical compound. Then you do breakfast -food in which a chemical compound is used as preservative, fertilizer, coloring agent. Then you go to office by wearing a shoes -made by polymer a chemical compound. when you feel uncomfortable or when you feel pain, you take a painkiller pills - a chemical compound. In general  you start your day with chemical and also end...