1. Chapter 4: Atomic Structure 4.1: Defining the Atom

2. I. Early Models A. Dalton’s atomic theory: –1. All elements made of atoms (True) –2. Atoms of same element identical (False – Isotopes) –3. Different atoms combined to form compounds (True) –4. Chemical reactions happen when atoms joined, separated, or rearranged (True) –5. Atoms of one element can’t be changed into others through chem. rxn. (False – Nuclear Rxns)

3. II. Atomic Size A. Atom: smallest particle of element that still has same properties B. 100,000,000 copper atoms = 1 cm across Scanning Tunneling Microscopes can see individual atoms Iron atoms placed in a ring on Gold

4. 4.2 Structure of the Nuclear Atom

5. I. Electrons (e - ) A. Very small, negatively charged atomic particles B. Discovered by J.J. Thomson with Cathode Ray tube C. Electric current sent through gases in tube, light beam attracted to opposite charges, repel by same charge Positive Magnet Negative magnet

6. II. Protons and Neutrons A. Protons: + charged particles, larger than e - B. Protons discovered in cathode ray tube when repelled by positive charge C. Neutrons: no charge, ~ same size/mass as proton Carbon Atom Protons Neutrons Electrons

7. III. Atomic Nucleus A. Most thought atoms were evenly spread + and - B. Rutherford shot alpha particles through Gold foil C. Expected particles go through because of spread out + charge, but some even deflected straight back. D. Must be clusters of mass (Nucleus)! http://www.youtube.com/watch?v= 5pZj0u_XMbc

8. E. Nucleus: center of mass, protons and neutrons F. Electrons surround nucleus Proton Neutron Electron Nucleus

9. 4.3: Atomic Differences

10. I. Atomic Number A. Atomic #: number of protons in atom B. Atoms have no overall charge C. So, number of protons and electrons are equal D. Smaller value number on periodic table Atomic Number

11. II. Mass Number A. Mass #: Total number of Protons and Neutrons B. Average of atomic mass for most common form of element (round it off) C. # of Neutrons = Mass # - Atomic # D. Larger value # on periodic table Mass Number rounded to 7 Ex. How many protons, neutrons and electrons does an atom of Sodium have? 11 protons, 12 neutrons, 11 electrons

12. III. Isotopes A. Isotope: atoms with same number of protons, but different numbers of neutrons B. Different mass numbers C. Example: Three forms of Hydrogen –1. “H –1” (one proton, no neutron) –2. “H –2” “Deuterium” (one proton, one neutron) –3. “H –3” “Tritium” (one proton, two neutrons)

13. IV. Atomic Mass A. Weighted average mass of an atom B. Represents the average of the masses of all isotopes of an atom considering their abundance C. Ex. H –1 is in the most common over H –2, H –3 so the mass is close to 1 (1.008)

14. V. Periodic Table Preview A. Periods: horizontal rows B. Groups: vertical columns (similar properties) Period Group