Examples of elements
Any element consists of only one kind of atoms. Gold consists of only gold atoms, a flask of gaseous nitrogen consists of only nitrogen atoms, and the lead of a graphite pencil consists of only carbon atoms.
If you take a piece of chalk and go on cutting it into smaller and smaller bits, you will come to a stage where you need a microscope to see the smaller dimensions. As you go further into smaller dimensions, you need very powerful microscopes to see the minuscule bits. There you will see that the chalk piece is made up of molecules. A molecule of chalk is made up of smaller parts − the atoms.
All atoms are made up of protons, neutrons and electrons(only exception: 1H1 doesn't have neutrons). It is the way these subatomic particles are arranged that gives each atom its unique characteristics. The electron arrangement (or configuration) gives each atom or element its chemical and physical characteristics. Thus, the number of protons or the atomic number (Z) identifies a particular element. Since an atom is electrically neutral, its number of electrons is equal to the proton number Z. For example, hydrogen is denoted as H and its atomic number (Z) = 1, and it has 1 electron. Helium is denoted as He and its atomic number (Z) = 2 and it has 2 electrons.
An element is a substance, which cannot be split into two or more simpler substances by the usual methods of applying heat, light, electric energy or even by chemical reactions. Pure gold, for instance, is an element because it consists of only gold atoms. Similarly, the element nitrogen consists solely of nitrogen atoms, and the element carbon solely of carbon atoms. When atoms combine, a molecule is formed. A molecule may be made up of same kind of atoms or different kinds of atoms. When atoms of the same element combine together, they may be monoatomic (Ex: Inert or Noble gases such as He, Ne, Ar etc), diatomic (Ex: H2, N2, O2 etc) or polyatomic molecules (O3, P4, S8 etc).