1. Midterm Review Chapter 3 Pg 74-104

2. Atomic Theory pg 74-78  Atomic Theory – the idea that atoms are the building blocks of all matter  Everything is made up of atoms

3. The Laws  The law of conservation of mass – states that mass is not created or destroyed in a reaction.  The mass of the reactants is equal to the mass of the products N + O = NO Mass of reactantsMass of Products N= 16 grams NO = ? O= 14 grams

4. The Laws  Law of definite proportions – states that two samples of a given compound are made of the same elements in exactly the same proportions by mass.  Example H 2 O (water)  No matter how much water you have (1g or 100g) it will always 89% O and 11% H

5. John Dalton  Developed atomic theory  Proposed idea that elements are composed of only one kind of atom

6. Structure of Atoms pg 79-89  Atoms can be divided into three different particles  Protons  Neutrons  Electrons

7. Atoms

8.  Nucleus center that is composed of protons and neutrons  Nucleus has an overall positive charge  Electrons are in orbitals rotating around the nucleus

9. Subatomic Particles  Protons – have mass of 1 amu and positive charge (+1)  Neutrons – have mass of 1 amu and neutral charge  Electrons – are considered massless and have a negative charge (-1)

10.  Atomic Number – the total number of protons in the nucleus of an atom  Mass Number – The sum of the number of protons and neutrons of the nucleus of an atom  Protons + Neutrons = Mass Number  Average atomic mass – the weighted average of the masses of all naturally occurring isotopes of an element

11. Isotopes  Isotopes – atoms that have the same number of protons (same element) but differing numbers of neutrons  Different number of neutrons changes the atomic mass

12. Electron Configurations pg 90 - 99  Pauli Exclusion Principle – Electrons in the same orbital have to spin in opposite directions  Aufbau Principle – Electrons fill orbitals starting with lowest energy level  Hund’s Rule – If energy levels have multiple orbitals, each orbital has to have one electron before any orbital has two electrons

13.  https://www.youtube.com/watch?v=SoNI QjW5Zxs