AP Chem Chapter 2

AP ChemChapter 2

Elements Compounds amp 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 ishellip Salt

Silver

Sand

Salt Water

Section 2 Law of Conservation of Mass

Law of Definite Proportions

Law of Multiple Proportions

Daltonrsquos Atomic Theory Very Important The foundation upon

which chemistry is built

Know the 4 postulates

Understand how they relate to the Laws

Section 4mdashChemical History JJ Thompson

Discovered the masscharge ratio for a particle that was over 11000th times smaller than a Hydrogen atomhellipknow 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 -1602 x 10-19C

In relative terms that charge is -1

MassCharge ratio Since we now know the charge we can

multiple the charge times the masscharge ratio to find the mass of the electron

The mass of the electron is 9109 x 10-28 g

In relative terms it has a mass of 0 because protons and neutrons are 1840 times as massive and they have a relative mass of 1

Mass of a Proton A proton has a mass of 166 x 10-24 g

A neutrons mass is slightly more

1 amu = approximately the mass of a proton

1 amu = 112 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 gramshellip 12 amu (166 X 10-24 g amu) = 1992 X 10-23 g

To find the mass of a mole of C atom multiply x Avogadrorsquos number 1992 X 10-23 g x 602 X 1023 = 120 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 Rutherfordrsquos 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

cationnonmetal 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

Coulombrsquos 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 in charges means more energy in the bond 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 ldquoateiterdquo 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 ldquotied uprdquo 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 26 on pg

69) NO2 is nitrogen dioxide (no mono prefix is

needed if itrsquos the first element) You name both elements but add ndashide 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 to nitrite so ndashite) Name is nitrous acid Use the root of the anion add ndashous suffix and acid

HNO3 (bonded to nitrate so ndashate) Name is nitric acid Use the root of the anion add ndashic 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 Alkanesmdashall C-C single bonds

Ends in -ane Alkenesmdashcontains at least 1 C-C double bond

Ends in -ene Alkynesmdashcontains at least 1 C-C triple bond

Ends in -yne

1 lt 2 lt 3 and a lt e lt y

Aromaticmdashcontains at least 1 benzene ring

To Namehellip 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 complicatedhellip Itrsquos 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 ldquofunctional grouprdquo A functional group always reacts the same no

matter WHAT ELSE is attached to it We use R- to represent some ldquorandom organic

fragmentrdquo which is attached to the functional group but which we really donrsquot 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 Itrsquos 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 = 34218 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