1. A.P. Ch. 2 Review Work
Atoms, Molecules, Ions

2. Conservation of mass: during a reaction the amount of material you start with equals the amount you end with

3. Dalton’s Atomic Theory
1. Elements made of atoms (True)
2. Atoms of same elements identical, different elemental atoms are different (False, Isotopes)
3. Compounds are atoms combined (True)
4. Chemical rxns: reorganization of atoms (True)
5. Cannot change one element into another through chemical rxn (False, Nuclear Rxns)

4. Thomson’s Experiment
Electrified gas in a cathode ray tube sends a beam from cathode (- end) to anode (+ end)
When a positive charge is presented to the light beam, it is bent towards charge
Thomson reasoned beam made of negatively charge particles he called “electrons”
Identified their charge to mass ratio
Positive Magnet

5. Rutherford’s Experiment
Used radioactive particles shot at a piece of gold foil to determine the composition of atoms
Based on “Plum-Pudding Model” of atom, assumed particles go through with few deflections

6. Most particles went through, yet some large deflections, indicating atoms made of mostly space with dense part

7. Atomic Particles Protons: positively charged in nucleus
Neutrons: no charge in nucleus
Electrons: negatively charged around nucleus

8. How Many Protons, Neutrons, and Electrons?
115B 157N Na+

9. Molecules Multiple atoms joined together by covalent bonds
Covalent bond: e- shared by attached atoms
Ionic bond: electrostatic attraction between oppositely charged ions (when e- lost or gained by an atom), different elements joined form “compounds”
Lose e- (+ ion “Cation”)
Gain e- (- ion “Anion”)
Ionic bond
Covalent bond

10. Periodic Table Organized by # of protons
Vertical columns (“groups”) based on similar properties
Horizontal rows (“periods”) based on similar electron organizations

11. Determining Ionic Charges
Based on periodic table location
Atoms are more stable with optimum number of electrons in their outer orbits (usually 8)
They can take in electrons to reach this # or lose some to make their next inner orbit full
Outer e-
Charge /