Robert Boyle:

1

• Robert Boyle
• An element is a substance which cannot be broken
  into simple substances by chemical means.
• Modern definition of an element
• An element is a substance composed of atoms with
  the same number of protons.
• John Daltons Atomic Theory
• Elements are made up of identical atoms.
• The atoms of the elements are immutable
• 3. Compounds form when the atoms of two or more
  elements combine in an integer ratio.