Do atoms of the same element differ in chemical properties?
No. Atoms of the same element have the same chemical properties.
How would atoms of the same element be different and would these atoms have different chemical properties?
A substance that is formed from atoms with a characteristic set of physical and chemical properties is called what?
A natural chemical element may be monoisotopic or has isotopes. Isotopes are atoms but they differ from other isotopes by the number of neutrons. This involve a different atomic mass and different physical properties or sometimes (for light isotopes) different chemical properties. Also, all chemical elements have radioactive, artificial isotopes.