AP Chemistry

Review:

Big Idea #1 MRS. BRAYFIELD

Review before we start…

Significant figures:

Nonzero integers count as significant

Leading zeros precede all nonzero digits and are not

significant

Zeros between nonzero digits are significant

Trailing zeros ARE NOT significant

Apparently some college rules are different…..

Exact numbers never limit the number of significant

figures in a calculation

Significant figures in calculations

For multiplication and division, the number of sig figs is

the same as the measurement with the least number of

sig figs

For addition and subtraction, the number of decimal

places is the same as the measurement with the fewest

number of decimal places

Big Idea #1

The chemical elements are fundamental building

materials of matter, and all matter can be

understood in terms of arrangements of atoms.

These atoms retain their identity in chemical

reactions.

Chapters in Book

Refer to chapters 1, 2, 3, 4, 7, 8

Atomic Structure

John Dalton

His model had 4 parts:

Each element is made of atoms

Atoms of a given element are identical

Atoms can combine to form compounds

These compounds have the same relative number and type of

atoms

Chemical reactions involve rearrangement of bonded atoms – do not change atoms

Dalton’s Laws

Law of Definite Proportion

A given compound always contains exactly the same

proportions of elements by mass

Law of Multiple Proportions

When two elements form a series of compounds, the

ratio of masses of the second element that can

combine with 1 gram of the first element can be

reduced to the smallest whole number

How we calculate empirical formulas

Atomic Structure

Dalton’s model of hard spheres was challenged

because of isotopes

Isotopes – atoms of the same element with different

numbers of neutrons (different masses)

Average atomic mass calculations

Take the percent abundance and multiply by the

weight

Mass Spectrometry

This is a technique to

determine the mass

spectrum of an element.

In this technique, a sample

is ionized and the fragments

are passed through a

sensor

Atomic Structure

Niels Bohr used line spectrums to develop his atomic

theory

Looks like a solar system

You have a nucleus that is orbited by electrons

Electromagnetic Radiation

From shortest to longest:

Gamma rays, x-rays, ultraviolet, visible, infrared, microwave, and radio

Electromagnetic radiation can acts as particles and

waves

Electromagnetic Radiation

𝑣 = 𝑐/𝜆

v = frequency; c = speed of light; λ = wavelength

We can quantize light:

Δ𝐸 = 𝑛ℎ𝑣

Where E is energy, n is integer (quantum number), h is Planck’s constant, and v is frequency

𝐸𝑝ℎ𝑜𝑡𝑜𝑛 = ℎ𝑐/𝜆

Atomic spectrum – it shows us the absorption lines

for an element

Quantum Mechanical Model

The quantum mechanical

(QM) model shows us the

three dimensions of the

wave functions

This is the mathematical

probability of finding

electrons in the electron

cloud

Structure of Atom

Subatomic particles (proton, neutron, electrons)

Coulomb’s Law:

𝐹 = 𝑘𝑞1𝑞2

𝑟

Where F is force, k is a constant, q is charge, r is

distance

Coulomb’s Law shows us the force that holds the atom

together

Photoelectron Spectroscopy

Photoelectron spectroscopy (PES)

is a technique that can be used

for electron shells in an atom

Light is shined on an atom and the

minimum frequency needed to

remove an electron is determined

From this data, you can find the

ionization energy

Electrons further away from the

nucleus need less energy than

ones close to the nucleus due to

shielding

PES

To read the graph of PES, it shows the relative

number of electrons that come off at different

energies

BASICALLY, it is a pictorial diagram/graph of the

electron configuration and how ionization energies

relate

http://www.chem.arizona.edu/chemt/Flash/photoe

lectron.html for simulation

http://www.adriandingleschemistrypages.com/ap/s

ummary-of-additions-to-new-ap-chemistry-

curriculum-part-1-pes/ for questions

Quantum Numbers

There are four quantum numbers:

n: principle quantum number; related to size and

energy of the orbital

l: angular momentum quantum number; related to

shape of the orbital

ml: magnetic quantum number; related to the position

of the orbital in space

ms: electron spin quantum number; related to the spin

of the electron (only two values)

Quantum Numbers

Quantum number n

Values of 1, 2, 3, 4, etc.

Refers to the row number

Quantum number l

Values of s, p, d, f

Electron Configurations

Aufbau principle:

Fill lower orbitals first

For example

Config. for Oxygen:

To find # of valence

electrons, it’s the # of

electrons in highest level

6 for Oxygen

Periodic Trends

Atomic Radii

Decrease going across

Increases going down

Ionization Energy

Increases going across

Decreases going down

Electron Affinity

Increases going across

Decreases going down

Periodic Trends

Ionic Radii

Cations are smaller than parent

Anions are larger than parent

Matter on Macro Scale

Molar mass

The weight (in grams) of one mole of a substance

Percent composition

𝑀𝑎𝑠𝑠 𝑜𝑓 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝑖𝑛 1 𝑚𝑜𝑙 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑

𝑀𝑎𝑠𝑠 𝑜𝑓 1 𝑚𝑜𝑙 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑× 100%

Mixtures

Pure substances (element and compound)

Mixtures (homogeneous and heterogeneous)

How to separate mixtures (distillation, filtration,

chromatography)

Conservation

Atoms and therefore mass must ALWAYS be

conserved in any chemical reaction

Identifying Matter

Infrared spectroscopy

This measures the radiation absorbed by molecules

This is from different bonds absorbing different frequencies

Each molecule produces a unique spectra

Identifying Matter

UV-Vis spectroscopy

This measures the radiation

that double bonds absorb

Gravimetric Analysis and

Titration

Titrations with acids and

bases to reach an endpoint

Homework

http://www.cengagebrain.com/shop/isbn/97805471

25329

Go towards bottom of page and click “Free Materials”

Click “Access Now” to go to companion site

From the pull down menu select the chapter you wish

to view

Take the “Tutorial Quiz”

When finished, make sure to print out results or email them to me: rbrayfield@twinlakes.k12.in.us

Do chapters 1, 2, and 7