Announcements TEXTBOOKCLICKERS HOMEWORK LAB NEXT WEEK CHEMISTRY HELP

Announcements • TEXTBOOK/CLICKERS • HOMEWORK • LAB NEXT WEEK • CHEMISTRY HELP CENTER • ATTENDANCE SHEETS

Chapter 1: Matter and Measurement �Atoms and Elements �Molecules and Compounds �Classification of Matter �Properties of Matter and Measurement Temperature Mass Volume �Unit Analysis Calculations

The Periodic Table- It’s 140 This Year!

ATOM Smallest unit of matter ELEMENT Contains only 1 type of atom MOLECULE Contains >1 atom connected together COMPOUND Contains >1 atom connected together AND >1 type of element Pure Substances= Elements and Compounds

Classification of Matter

Clicker Question 1 Which of the following is a pure substance? a. b. c. d. Grain alcohol Sparkling water 14 -carat gold Chocolate chip

Clicker Question 2 What is a root beer float? a. b. c. d. Compound Element Homogeneous Mixture Heterogeneous Mixture

Let’s ponder the Root Beer Float some more… Root beer float deconstructed* Ice cream Sugar Cream Vanilla Root beer Carbonated water Water Carbon Dioxide Sugar Root extracts (sassafras, sarsparilla root, liquorice, anise, etc. ) *An homage to a great book, Twinkie Deconstructed, by Steve Ettlinger

Chapter 2: Modern Atomic Theory �Matter consists of atoms �Atoms consist of three fundamental particles, found in the nucleus and the space around the nucleus

Chapter 2 - Elements and Compounds Modern atomic theory All matter is composed of small particles called atoms Atoms are made up of three subatomic particles

Arrangement of Particles in the Atom Small nucleus contains nucleons: Positively charged protons Neutrons with no charge Vast majority of mass Outside the nucleus Negatively charged electrons Large volume of (mostly empty) space relative to nucleus

Atoms All atoms of an element have the same atomic number = number of protons In a neutral atom (no charge), the number of positively and negatively charged particles must be equal # protons = # electrons The mass number = protons + neutrons

Isotopes �Isotopes Atoms with same number of protons but different number of neutrons

Isotopes • When two atoms have the same atomic number (Z), but different atomic masses (A), they are called isotopes • Isotopes differ in the number of neutrons • ATOM SYMBOLS mass number→A atomic number→Z X 35 17 Cl 17 protons 35 -17=18 neutrons • EXAMPLE: How many neutrons does Molybdenum-90 have? 90 Mo 42 # protons=42 # neutrons= 90 -42=48

Isotopes Most elements have multiple isotopes 1 H, 2 H (deuterium), 3 H (tritium, radioactive) 79 Br, 81 Br 64 Zn, 66 Zn, 67 Zn, 68 Zn, 70 Zn Atomic mass is the mass of a single atom Average atomic mass takes into account isotopes and natural abundance We use atomic mass units (u) 1 amu = 1. 661 x 10– 24 g (about the mass of a proton)

It’s Time For Some Donut Math! Dunkin Donuts sells both regular-sized donuts and Munchkins Let’s say that of all the donuts sold: 78. 3% are regular-sized (mass= 57 g) 21. 7% are Munchkins (mass= 10 g) What is the weighted average mass of a Dunkin Donut?

Isotopes and Average Atomic Mass A Non-Edible Example Chlorine has two isotopes: Isotope Mass (u) % Abundance 35 Cl 34. 969 75. 78 37 Cl 36. 966 24. 22 What is the average atomic mass of Chlorine?

What do these things have in common? ! s e n H o m r o

Floyd Landis Case �Landis won 2006 Tour de France �Tested positive for testosterone doping �Does Landis have an high testosterone level? testosterone epitestosterone

Floyd Landis Case � Is the excess testosterone natural or synthetic? � Isotope-ratio mass spectrometry (CIR) used to determine the ratio of 13 C to 12 C in Landis’ testosterone � Photosynthesis prefers 12 C C 3 plants: Strong preference for 12 C C 4 plants: Less of a preference for 12 C � Normal diet= mixture of C 3 and C 4 plants � Synthetic testosterone comes from soy, contains less 13 C � 13 C: 12 C reduced �Landis positive for doping

What do these things have in common? ! s e n H o m r o

What holds an atom together? Coulomb’s Law of electrostatic interactions. General Behavior: Like charges repel. Opposite charges attract.

What holds an atom together? Coulomb’s Law of electrostatic interactions. If we double a charge from +1 to +2, the force will: 1. 2. 3. 4. Double Halve Quadruple Quarter

What holds an atom together? Coulomb’s Law of electrostatic interactions. If we double the distance, the force will: 1. 2. 3. 4. Double Halve Quadruple Quarter

What’s wrong with this picture? Electrons are held near the nucleus by the electrostatic attraction between them, but … The forces of nature:

We’re not just making it up! How could we possibly know that the nucleus is small compared to the size of the atom? Why not think the protons, electrons and neutrons are all mixed together? The Rutherford Experiment

We’re not just making it up! The Rutherford Experiment