Transcript General Chemistry 1 Sections 7-12

Announcements
•T E X T B O O K / C L I C K E R S
•H O M E W O R K
•L A B N E X T W E E K
•C H E M I S T R Y H E L P C E N T E R
•A T T E N D A N C E S H E E T S
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.
Grain alcohol
b.
Sparkling water
c.
14-carat gold
d.
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
35
17
X
Cl
17 protons
35-17=18 neutrons
• EXAMPLE:
How many neutrons does Molybdenum-90 have?
90
42
Mo
# protons=42
# neutrons= 90-42=48
Isotopes
 Most elements have multiple isotopes
 1H, 2H (deuterium), 3H (tritium, radioactive)
 79Br, 81Br
 64Zn, 66Zn, 67Zn, 68Zn, 70Zn
 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 = 1u = 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= 57g)
21.7% are Munchkins (mass= 10g)
 What is the weighted average mass of a Dunkin
Donut?
Isotopes and Average Atomic Mass
all isotopes
Average atomic mass =

(fractional abundance)  (mass of isotope)
A Non-Edible Example
Chlorine has two isotopes:
Isotope
Mass (u)
% Abundance
Cl
34.969
75.78
Cl
36.966
24.22
35
37
What is the average atomic mass of Chlorine?
What do these things have in common?
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 13C to 12C in Landis’ testosterone
 Photosynthesis prefers 12C

C3 plants: Strong preference for 12C

C4 plants: Less of a preference for 12C
 Normal diet= mixture of C3 and C4 plants
 Synthetic testosterone comes from soy, contains less 13C

13C:12C
reduced  Landis positive for doping
What do these things have in common?
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
We’re not just making it up!
The Rutherford Experiment