"Chemistry" Grade- 9 (New Course)
Unit -14 Atomic Structure and Chemical Bond Chemistry : The branch of Science consisting the study of matter is called chemistry . Matter :Any substance which occupies space and have mass is called mater .For example :air water, Hydrogen, stone etc. Element:Element: The pure substance which can not be converted or broken down into two or more simpler substance by any physical or chemical process is called element .There are about 118 elements in the nature .Out up these 92 elements are found in nature or formed naturally are called natural elements .Remaining 26 elements are man made , are called artificial elements . On the basis of chemical and physical properties elements are divided into 3 types :They are :i) Metal i.e. Iron ,gold , silver etc. ii.) Non metal : Hydrogen ,oxygen ,carbon ,etc. iii.)Metalloid: Arsenic, antimony etc. They are generally found in 3 states i.e. Solid e.g. :Gold ,silver , Liquid e.g.: Mercury ,bromine ,and Gas e.g.: Hydr