1. A TOMS Chapter 16 and 17 Physical Science Honors

2. D ALTON ’ S A TOMIC T HEORY Dalton (1766-1844) All matter is composed of atoms Invisible and indestructible Atoms of a given element are identical in size, mass and chemical properties Atoms of a specific element different from another element Different atoms combine in different ratios to form compounds In a chemical reaction, atoms are separated, combined, or rearranged.

3. A TOM S TRUCTURE Atom is the smallest unit of an element Subatomic Particles Protons and Neutrons make up the Nucleus Protons have a +1 Charge Electrons have a -1 Charge

4. A TOMS AND E LEMENTS Atomic Number Number of protons This defines the element Atomic Mass Number of protons and neutrons in the nucleus Most elements are found in a neutral state Number of Electrons are EQUAL to the number of Protons

5. W ITH YOUR N EIGHBOR # of Protons ____ # of Proton ____ # of Electrons _____ # of Electrons ____ # of Neutrons _____ # of Neutrons _____

6. Q UARKS Protons and Neutrons are made up of smaller particles called quarks There are six unique quarks Three make up the proton Three make up the neutron

7. A TOMIC M ODELS

8. E LECTRON C LOUD M ODEL 1926 Electrons exist in a cloud that surrounds the nucleus Electron cloud is 100,000 times larger in diameter than the nucleus Why do we use a cloud and not a specific location?

9. A CTIVITY IN YOUR N OTEBOOK Explain the difference between the Bohr Model and the electron cloud model? Using the periodic table in your textbook, Draw the elements hydrogen and helium using the Bohr model and the Electron Cloud model

10. A TOMIC N UMBER Atomic number is the proton number Proton number determines the type of atom or element Example: Any atom with 6 protons is a carbon atom Atomic number can tell you the name of the element, the number of protons as well as the atomic number

11. A TOMIC M ASS Atomic Mass: The weight of the protons and neutrons The unit of measurement is the atomic mass unit (amu) Defined as 1/12th the weight of a carbon atom

12. M ASS N UMBER Mass # = # of protons + # of neutrons You can calculate the number of neutron of an atom with the atomic number and the atomic mass Calculate how many neutrons Ni, Au, Pt, W, and O

13. O THER F ORMS OF E LEMENTS Ion total number of electrons is not equal to the total number of protons gives the atom or molecule a net positive or negative electrical charge Isotope An element is defined by its atomic number (number of protons) Mass of the element is the number of neutrons and protons Elements can have a wide range of neutrons This different mass number is called an isotope

14. A VERAGE A TOMIC M ASS Each element normally has more than one naturally occurring isotope Each element’s mass is described by an average It is the weighted average mass of all the naturally occurring isotopes of an element According to their natural abundances Example: 80 percent of boron is boron-11 20 percent of boron is boron-10 The weighted average is 10.8

15. T RENDS OF THE P ERIODIC T ABLE