1. Review Class #1

2.  Greeks ◦ Matter is made up of tiny, discrete particles  Fire, Earth, Wind, Water  Boyle ◦ Found gold and silver as being elemental  Dalton’s Theory ◦ All elements are composed of indivisible atoms ◦ All atoms of a given element are identical ◦ Atoms of different elements are different, that is, they have different masses ◦ Compounds are formed by the combination of atoms of different elements

3.  JJ. Thomson ◦ Cathode ray tube to show smaller units make up atom ◦ Light ray deflected in a magnetic field ◦ Came up with idea of electrons  PLUM PUDDING MODEL  Nucleus ◦ Rutherford  Bombarded atom with alpha particle  Alpha particle got deflected  Concluded atoms have a dense core – NUCLEUS  Because particles repelled, nucleus must be positive too  Also concluded atom is mostly empty space  Electrons are distributed in the empty space

4.  Bohr ◦ Dense nucleus ◦ Electrons found in orbits  Electrons have required energy to keep them in orbit  Not too much or too little  Called this the planetary model  Wave Mechanical Model – modern model ◦ Energy and matter can act as waves and particles  Solar panels ◦ Dense positive center ◦ Electrons are in “regions of probability”

5.  RB pg. 4, 1-12

6.  Nucleus contains 2 types of particles ◦ Neutrons and protons  This is where the mass comes from  Subatomic particles ◦ Mass of a proton is found on 1 st page of reference tables ◦ 1 amu = mass of a proton = mass of 1 proton ◦ Mass of electron is negligible

7.  Sum of number of protons and neutrons equals the mass number ◦ Found in the periodic table as atomic mass ◦ Measured in amu (atomic mass units) NOT grams  If measured in grams would be atomic mass * mass of an atom

8.  All type of element on periodic table have the same number of protons ◦ Protons define the element  Neutrons can vary from atom to atom for 1 element ◦ Same # protons but different number neutrons = isotopes  Examples: ◦ Carbon – 12 = 6 protons and 6 neutrons ◦ Carbon – 13 = 6 protons and _ neutrons

9.  Mass number for element must be integer ◦ We can’t have part of a proton or neutron ◦ Why are atomic masses of elements not integers?  Weighted atomic mass ◦ The atomic mass is an average of all the different isotopes. ◦ If have of the carbon isotopes were carbon 12 and half were carbon 13  Weighted atomic mass would be 12.5  Is this the weighted atomic mass for carbon?  Which isotope is more abundant?

10.  Found in space around a nucleus of an atom  Energy Levels ◦ Orbitals in an atom form series of energy levels  S holds 2 electrons  P holds 6 electrons  D holds 10 electrons  This is where S, P, and D block names come from  Electrons can move between energy levels ◦ You can walk up a set of stairs, takes a certain amount of energy ◦ Certain amount of energy is needed for e- to jump between energy levels (it is quantized)

12.  Ground state – e- in lowest energy ◦ Ground state is given in periodic table on ref. tables ◦ If e- configuration doesn’t match ground state, it has to be excited state  Excited state ◦ Electrons possess more energy than they would if they were in ground state  Spectral lines ◦ Visible light that is emitted when electrons fall back to their ground state ◦ Must first add energy to be excited – we can’t see this

13.  RB pg. 7, 13-36