1. Atomic Structure

2. Elements l Only about 118 different elements make up all the materials we know çGreater than 99% of matter on earth is formed by about elements çLife – mostly ç is most abundant element in universe

4. First Photo of Individual Atoms l Photo made in 1970 with a scanning electron microscope by researchers at the University of Chicago's Enrico Fermi Institute. l Strings of dots are chains of thorium atoms.

5. Atoms Arranged with STM l Xenon on nickel l HAL

6. 48 Iron Atoms on Copper Crystal l Iron atoms positioned into a circular ring that “corrals” electrons. l Taken with a scanning tunneling microscope at the IBM Almaden Laboratory in San Jose, CA.

7. Atom l Smallest particle of an element that maintains the properties of the element l Greek origin – atomos which means indivisible l In particle accelerators and in stars, subatomic particles can be found l Atoms composed of protons, neutrons, and electrons çActually, protons and neutrons can be further split into quarks

8. Atomic Structure l Electrons l Protons l Neutrons l Atoms l Protons and neutrons çSince like charges repel, how are the protons bound together in the nucleus? » l Electrons l Why are neutrons needed? ç

9. Atomic Size & Recyclability l About 10 23 atoms in a thimbleful of water l Perpetually moving Perpetually moving çDiffusion çAbout 6 years for one of your exhaled breaths to become mixed in the atmosphere As many atoms in a breath of air as breathfuls of air in Earth’s atmosphere

10. Atomic Scale l Toyota – Dorito Model çNucleons (protons and neutrons) are like toyotas (2000 lb cars) çElectrons are like bags of doritos (1 lb objects) çDoritos are orbiting the cars at a distance of a few miles l (Nucleus) BB on the 50 yard line with the electrons at a distance of about 50 yards from the BB l Atom is mostly empty space l Size is electronic

11. Atomic Scale

12. Atomic Mass Unit l Atomic Mass Unit: amu l approximate mass of a single proton or neutron is 1 amu l mass of an atom in atomic mass units is simply the sum of its protons and neutrons and is known as the atomic mass number l mass of an electron is so small that it's disregarded

13. Isotopes l number of protons in a nucleus l all hydrogen nuclei have a single proton but most have no neutrons. çsome contain l most iron nuclei with 26 protons contain 30 neutrons l Atoms of the same element that contain different numbers of neutrons are isotopes

14. Electrons l Cathode Rays çDeflected by charged particles çDeflected by magnetic field J.J. Thomson 1856-1940

15. Charge on Electron l Determined charge on electron l Millikan Oil Drop Experiment Robert A. Millikan 1868 - 1953

16. Nucleus l Rutherford’s Gold Foil Experiment l Deflection of alpha particles showed the atom to be mostly empty space with a concentration of mass at its center Ernest Rutherford 1871 - 1937

17. Quarks Make Up Nucleons l Proton: 2 ups + 1 down l Neutron: 2 downs + 1 up

18. AntiMatter l antimatter is composed of atoms with negative nuclei and positive electrons, or positrons l positron has the same mass as an electron and the same magnitude of charge but the opposite sign. l antiprotons have the same mass as protons but are negatively charged

19. Other Terms l Element -- l Compound: chemical combination of elements l Mixtures l Molecules: smallest particle of a compound that has all the compound's chemical properties. Atoms combine to form molecules

20. Dark Matter l Unseen and unidentified matter l evident by its gravitational pull on stars in the galaxies l composing perhaps 90 percent of the matter of the universe