1. Particles of Matter
Chapter 1.3

2. Atom
The smallest particle of an element.

3. John Dalton British school teacher
In 1802 he proposed an atomic theory
Dalton tested his ideas by carrying out experiments

4. Dalton’s Atomic Theory 1
Atoms can’t be broken into smaller pieces
Dalton imagined atoms to be like tiny marbles or rigid spheres that are impossible to break

5. Daltons Atomic Theory 2 In any element, all the atom are exactly alike
This idea explains why an element always has the same properties

6. Dalton’s Atomic Theory 3
Atoms of different elements are different
This idea explains why different elements have their own set of properties

7. Dalton’s Atomic Theory 4
Atoms of two or more elements can combine to form compounds
Compounds can be broken down into elements, so Dalton concluded that compounds had to be made of atoms.

8. Dalton’s Atomic Theory 5
Atoms of each element have a unique mass.
Dalton and other scientists of his day were not actually able to measure the mass of individual atoms

9. Dalton’s Atomic Theory 6
The masses of the elements in a compound are always in the same ratio
Water is a compound composed of hydrogen atoms and oxygen atoms, always in the ratio 2 hydrogen to 1 oxygen.

10. Atoms Atoms are super tiny
One grain of sand has more atoms than there are grains of sand on the entire beach
A drop of water has 2,000,000,000,000,000,000,000 atoms of oxygen and twice as many atoms of hydrogen
There is now a scanning tunneling microscope that can capture what atoms look like

11. Atom and Molecules
Atoms can link with each other. A chemical bond holds two atoms together.
A molecule is a combination of two or more atoms that are bonded together
Example: Water molecule, acetic acid molecule (C2H4O2)