Question: what are the three important properties of chemical elements?
Answer: Atomic number. The atomic number indicates the number of protons within the core of an atom. ... 
Atomic mass. The name indicates the mass of an atom, expressed in atomic mass units (amu). ... 
Electronegativity according to Pauling. ... 
Density. ... 
Melting point. ... 
Boiling point. ... 
Vanderwaals radius. ... 
Ionic radius.