AP Chem
Chapter 2
Elements Compounds &
Mixtures
 Elements

On the Periodic Table
 Compounds


Ionic (metal bonded to nonmetal)
Molecular (2 nonmetals bonded together)
 Mixtures


Homogeneous = Solution = 1 phase
Heterogeneous = more than 1 phase
What is….?
 Salt
 Silver
 Sand
 Salt
Water
Section 2
 Law
of Conservation of Mass
 Law
of Definite Proportions
 Law
of Multiple Proportions
Dalton’s Atomic Theory
 Very
Important. The foundation upon
which chemistry is built.
 Know
the 4 postulates
 Understand
how they relate to the Laws.
Section 4—Chemical History
 JJ



Thompson
Discovered the mass/charge ratio for a
particle that was over 1/1000th times smaller
than a Hydrogen atom…know to be the
least massive atom.
He concluded that this particles helped
make up the atom.
Plum Pudding Model
Oil Drop Experiment




Used X-rays to knock electrons off of gas
molecules.
Oil droplets fell through this area and the
electrons would stick to the drop.
He could measure the mass of the drop by its
rate of falling.
By turning on an electric field that the drop
was falling through, he could make the drop
slow down, stop, or even move back up.
Oil Drop Experiment
 In
other words, the charged drop was
repelled by the electrical charge.
 Millikan
was able to calculate the charge
and found that the charge was always a
whole number multiple of -1.602 x 10-19C.
 In
relative terms, that charge is -1.
Mass/Charge ratio

Since we now know the charge, we can
multiple the charge times the mass/charge
ratio to find the mass of the electron.

The mass of the electron is 9.109 x 10-28 g.

In relative terms, it has a mass of 0, because
protons and neutrons are 1,840 times as
massive, and they have a relative mass of 1.
Mass of a Proton
A
proton has a mass of 1.66 x 10-24 g.
A
neutrons mass is slightly more.
1
amu = approximately the mass of a
proton.
1
amu = 1/12 of a C-12 atom
Mass of Carbon
1
atom of C-12 has a mass of 12 amu.
1
mole of C-12 has a mass of 12 g.
 Mass

of 1 C atom in grams…
12 amu (1.66 X 10-24 g/ amu) = 1.992 X 10-23 g
 To
find the mass of a mole of C atom, multiply
x Avogadro’s number.

1.992 X 10-23 g x 6.02 X 1023 = 12.0 g.
Gold Foil Experiment
 Rutherford
discovered the nucleus.
 Rutherford
was investigating the behavior
of alpha particles.
 However,
his discovery changed our
notions of the structure of the atom.
Gold Foil Experiment
 Rutherford
is also credited, by some, with
discovering the proton as well.
 James
Chadwich discovered the neutron
in 1932.
 Actually
the gold foil experiments were
carried out by Geiger, who worked in
Rutherford’s lab.
Section 5

Mass number
Atomic Number
Average Atomic Mass
Isotopes
Calculating Average Atomic Mass

Isotope notation

A fresh look at atomic theory in light of about
100 years of new discoveries.




The Periodic Table
 Big
Fat Review at the table in the back.
Section 7: review of bonding
 Ionic
compounds (metal cation/nonmetal
anion or polyatomic ion)
 Criss Cross
 Simplify if necessary
 Name by naming ions



Metal = same as element
Nonmetal = root of word + -ide suffix
Polyatomic = name of polyatomic ion
Coulomb’s Law
 Energy



= k q1 x q2 / distance
k is a constant
q are charges of the two ions
Distance is the distance between the two nuclei.
 Increase
bond

in charges means more energy in the
So MgO has more than NaCl
 Decrease

in distance means more energy
So NaCl has more than RbI, because the ions are
smaller and therefore can get closer to one another.
Know Common Charges
 Monatomic
ions (consult the periodic table)
 Polyatomic
ions: pretty much have to memorize
(pg 68)
 Remember
that ammonia (NH4+1) is the only
polyatomic cation.
 Remember
“ate/ite” rule.
Know Common Charges

Transition metals have multiple charges (also called
oxidation numbers or oxidation states)

Cr is +2, +3, or +6.




Cr+2 is chromous or chromium (II)
Cr+3 is chromic or chromium (III)
Cr+6 is chromium (VI)
Remember that a polyatomic ion is a group of ions
(bonded covalently to each other) and the overall
group has an ionic charge.
Hydrates
 Means
that water is “tied up” as a part of
the crystal structure.
 CuSO4·
5 H2O is copper (II) sulfate
pentahydrate. That is the correct name.

If you heat it and drive off the water (which
ought to be there), we then say that we
have anhydrous copper(II) sulfate.
Covalent compounds
 Two
nonmetals bonded together
 Use prefixes in the name (Table 2.6 on pg
69).
 NO2 is nitrogen dioxide (no mono prefix is
needed if it’s the first element). You name
both elements, but add –ide to the root of
the second element.
 N2O is dinitrogen monoxide (if mono is for
the second element, you must use it).
Acids: Look at the anion the H is
bonded to! Remember: H in front
of the formula = acid!
 HCl


(bonded to chloride, a monatomic ion)
Name is hydrochloric acid
Hydro prefix, -ic suffix and add acid
 HNO2 (bonded


Name is nitrous acid
Use the root of the anion, add –ous suffix and acid
 HNO3


to nitrite, so –ite)
(bonded to nitrate, so –ate)
Name is nitric acid
Use the root of the anion, add –ic suffix and acid
Simple Organic Compounds:
New from Last Year

Prefixes












Meth = 1 carbon
Eth = 2 carbons
Prop = 3
But = 4
Pent = 5
Hex = 6
Hept = 7
Oct = 8
Non = 9
Dec = 10
Undec = 11
Dodec = 12
Types of Hydrocarbons
 Alkanes—all

C-C single bonds
Ends in -ane
 Alkenes—contains

Ends in -ene
 Alkynes—contains

1
at least 1 C-C double bond
at least 1 C-C triple bond
Ends in -yne
< 2 < 3 and a < e < y
 Aromatic—contains
at least 1 benzene ring.
To Name…
 Find
the longest continuous carbon chain
 Determine what type of hydrocarbon it is for the
suffix.
 Number the chain so that any substituents
(things attached to the chain) have the lowest
possible numbers.
 Keep adding prefixes to the front of the name
until everything has been named. Use numbers
to specify WHICH carbon the substituent is
attached to.
Sound complicated?…





It’s not. Organic naming is very fun, but it can get
pretty hairy.
There are millions of different organic compounds, so
we had to come up with some way to classify
everything.
We do this by a concept called “functional group.”
A functional group always reacts the same, no matter
WHAT ELSE is attached to it.
We use R- to represent some “random organic
fragment” which is attached to the functional group,
but which we really don’t care about right now.
Draw the structure
 2,
2-dichlorobutane
 2,
3-dimethyl propane
 2-pentene
(2 specifies the position of the
double bond)
 Cyclohexane
Mixtures
 Heterogeneous
 Homogeneous


= solutions
Solutions are very important this year
ALL over the AP exam
 Review
physical separation techniques, especially
distillation and chromatography.



TLC = thin layer chromatography
GC = gas chromatography
HPLC = high pressure liquid chromatography
Mass Spectrometry = Mass
Spec
 Used
to determine masses of elements or
compound very accurately. Used a lot in organic
chemistry.
 Compounds sometimes break into fragments,
especially larger organic molecules.


Analyzing the possible fragments gives you insight
into the overall structure of the molecule.
It’s like putting together a puzzle.
Mass Spectrometry = Mass
Spec



Basically the sample is ionized by bombarding it with
high energy electrons.
An electron is pried off and we now have a cation.
Same mass, but it now has charge (remember, an
electron has no mass). But the fact that it is charged
now is very useful.
The charged particles are passed through an electric
field (which accelerates them) and a series of slits
(which focuses the beam of ions)

Although they have the same energy, since they have
different masses, they are moving at slightly different
speeds. This causes them to begin to separate themselves,
by mass.
Mass Spectrometry = Mass
Spec

The charged particles are then passed through a
magnetic field which attracts the particles.



Lighter particles move closer to the source; heavier
particles not so much.
They continue to separate by mass. They literally separate
into separate streams of ions, each one with a different
mass.
They then hit a detector which records where they hit
and the relative amount that hit each spot. The
relative amounts are an indication of % abundance.


Where they hit is then compared to known substances with
known mass that hits those same spots.
Using this information, you can determine the mass of your
sample, and the relative abundances, very accurately.
Molar Mass
 Simply
add up the masses of each element in the
formula, multiplying by any subscripts if
necessary.
 For example Al2(SO4)3 has




2 Aluminum atoms
3 Sulfur atoms
12 Oxygen atoms
MM = 342.18 amu or g
 Amu
if we are talking about 1 atom or molecule
 Grams if we are talking about 1 mole of atoms or
molecules.
The End
 See
you in Chapter 3 on Weds.
 Quiz
on Weds over Naming and Writing
Formulas