The number of well-known elements up till now is 118 elements, These elements can be classified according to their properties and electronic structure into metals, nonmetals and noble (inert) gases, In the 19th century,...
The molecules and the matter The molecules of one substance are alike in properties, but they differ from other substance molecules, the molecule is composed of tiny structural units called the atoms, A molecule...
The inert gases are the elements in which the outermost electron shells are completely filled with the electrons, so they don’t participate in any chemical combination in the ordinary conditions.
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.
