What is a chemical element ?

Chemical elements correspond to the different atoms occurring in the natural world. The chemical properties of element is defined by the number of protons in the atomic nucleus. Gold is made up of atoms with 79 protons. The atomic nucleus of oxygen has eight protons, hydrogen has only one. The atomic shell has exactly as many electrons (negative charge) as number of proton in its nucleus. 

How many elements are there  ?

To date there are 1118 elements exist in nature. Newly discovered elements :-

Nihonium (atomic number 113),

Moscovium (atomic number 115), 

Tennessine (atomic number 117), 

)ganesson (atomic number 118).