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John Dalton’s Atomic Theory (1803)

• All matter is built from about 100
• elements.
• Elements are substances that cannot be
• broken down into simpler components by chemical reactions –consist of particles
• called atoms
• Atoms of an element are all the same for
• that element e.g. Au foil/dust/atom would have the same
• chemical properties
• There are only 92 elements that occur
• naturally on earth made up from only 92 different types of atoms.
• First
• person to assign chemical symbols to the different elements.
• Noticed
• that elements hydrogen and oxygen always combined together in fixed
• proportions-proposed that:
• All matter is comprised of tiny
• indivisible particles called atoms;
• Atoms cannot be created or
• destroyed;
• Atoms of the same element are
• alike in every way;
• Atoms of different elements are
• different;
• Atoms can combine together in
• small numbers to form molecules