1.  Suggested Reading pgs.. 67 - 71 Pages 66-70 Chapter 3, Section 1 - Atoms STM (scanning tunneling microscope) image of a single zigzag chain of cesium atoms (red) on a gallium-arsenide surface (blue)

2.  450 B.C. Greek - Democritus  “All matter is composed of tiny, indivisible particles”  Atomos means Indivisible  This idea is not related to a measurable property … it can’t be experimentally tested Early Models of the Atom

4.  The transformation of a substance into one or more new substance. With new chemical and physical properties.  Reactants  Products Chemical Reaction

5.  States that mass is neither created nor destroyed during ordinary chemical reactions or physical changes. Law of Conservation of Mass

6. 4 g 32 g 36 g 4 H 2 O 4 H 2 O  total mass stays the same  atoms can only rearrange

7.  A chemical contains the same elements in exactly the same proportions by mass, regardless of the size of the sample, or the source of the compound. Law of Definite Proportions:

8. Salt - NaCl is always 39.34% Sodium and 60.66% Chlorine

9.  When elements combine, they do so in small whole number ratios. (non-metals) Law of Multiple Proportions:

10.  The smallest unit of an element that retains the chemical identity of that element.  There are about 110 different kinds of atoms that combine to form all matter. Atom

11. Dalton’s Atomic Theory – Early 1800’s  All matter is composed of atoms.  Atoms of a given element are identical, but are different from atoms of other elements.  Atoms cannot be subdivided, created, or destroyed.

12. Dalton’s Atomic Theory – Early 1800’s  Atoms of different elements combine in simple whole-number ratios to form chemical compounds.  In chemical reactions, atoms are combined, separated, or rearranged.

13. Dalton’s Atomic Theory – Early 1800’s

14. Revisions to Dalton’s Atomic Theory  Atoms are divisible into smaller particles called subatomic particles.  A given element can have atoms with different masses, called isotopes.

15. Scanning Tunneling Microscope  STM – provides “close” to a 3-D picture of atoms – that’s the best we can see, even today. STM picture of Nickel atoms