SAT Chemistry Study Guide

Structure of matterAtomic Structure

About Atoms Early Greek notion of earth, wind, fire, water as basic components of matter Indivisible particle “atom” from Greek “atomos” meaning indivisible Two main forces hold atoms together.

o The electric force holds the electrons in orbit around the nucleus. Opposite charges attract, so the electrons are drawn to the protons in the nucleus.

o The nuclear force holds the protons and neutrons together.

Experimental Evidence of Atomic Structure John Dalton’s Atomic Theory (1800s)

o All matter composed of atomso All atoms of an element alike (not necessarily true—isotopes)o Compounds = atoms combination in fixed proportions (AxByCz)o Chemical reaction = rearrangement of atoms; not created/destroyed

JJ Thomson’s Cathode Ray (1897)o Cathode ray bent by electric/magnet field; must have negative charged particleo Evidence for electron

Ernest Rutherford’s Gold Foil Experiment (1911)o Alpha particles come out of different directions when pass through foilo Evidence for nucleus

James Chadwick (1932)o Alpha particles shot at beryllium emitted weird neutral radiation that could know

protons out of other atomso Evidence of neutron, a heavy particle

Robert Millikan’s Oil Drop Experiment (early 1900s)o Charged oil drops fell through electric field at certain rateso Determined mass and charge of electrons on the oil drops

Quantum Numbers and Energy Levels (orbitals) Shape of the electron cloud, or orbital, depend on the amount of energy, angular

momentum and magnetic moment of the individual electron. 1. Principal quantum number = n =energy level; can be any integer

o lower energy orbits are close to the source of attraction. o The more energy you give a body in orbit, the further 'out' it goes. o If you give the body enough energy, it will leave the system entirely.

2. Angular momentum quantum number = l = shape of cloud/sublevel that electron is in; any integer from 0 to n-1

o ℓ = 0 = s orbital. spherical, centered on the nucleus. o ℓ = 1 = p orbital. usually polar, 2 teardrop petal shapes with the point towards

the nucleus, single plane

o ℓ = 2 = d orbital. similar to the p orbital shape, but with more 'petals' like a clover leaf. can also have ring shapes around the base of the petals.

o ℓ=3 = f orbital. similar to d orbitals, but with even more 'petals'. 3. Magnetic quantum number = ml = specific orbit of each sublevel; integer from -l to +l 4. Spin quantum number = ms = spin of electron (clock/counter); -1/2 or ½

Hybridization

Electron Configuration Fill in this order: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f14 6d10 7p6

Effective Nuclear Charge All e- are attracted to positive nucleus and repulsed by other electrons Effective Nuclear Charge = Zeff = Z –S

o Z = # of protons in nucleuso S = # of non-valence e-

Larger Zeff = smaller radius because more attraction of outer most e- to nucleus over repulsion by other e-.

o Pulls in outside e- closero Closer outside e- = smaller raidus

Periodic Trends Ionization energy

o Right increasing first, down decreasing after O ion energy larger than Cl

o amount of energy required to remove an electron from a neutral atom in its gaseous phase

o opposite of electronegativityo factor that affects ionization energy is electron shieldingo noble gases possess very high ionization energies because of their full valence

shell Electronegativity

o Same direction as ionization energyo atom's strength to attract and form bonds with electrons for full octeto Transition metals—little variance in value as move across and down noble gases

—full octet; lanthanides and actinides—no trend Electron affinity

o Same direction as ionization and electronegativityo ability of an atom to accept an electron

Atomic Radiuso Opposite direction as everything elseo O smaller than Cl

o

Nuclear Reactions Radioactivity is spontaneous break-up of unstable nucleus, and the resulting emission to

achieve stabilityo Stable nucleus has 1 to 1 ratio of proton to neutron

Alpha Decay: emit positive particle 42He

o Decreases proton count/atomic number by 2o Decreases atomic mass by 4

Beta Decay: emit negative particle -10e (or -1

0β)o Increase atomic number by 1o Nothing to atomic mass

Positron Emission: emit positive particle that is size of electron 10e

o Decrease atomic number by 1o Nothing to atomic mass

Fusion vs Fission Both releases tons of energy Fusion reactions

o two light nuclei are combined to form a heavier, more stable nucleus Fission Reaction

o heavy nucleus is split into two nuclei with smaller mass numbers

Valence Bond Theory two atoms will form a bond when there is orbital overlap

o a maximum of two electrons can be present in the overlapping orbitalso as pair of electrons is attracted to both atomic nuclei, a bond is formed, and as the

extent of overlap increases, the strength of the bond increaseso there is an equilibrium point where electronic energy is at min, bond is strongest

too much overlap/too little = energy increase hybridization- blending atomic orbitals to create energy level in between those of the lone

orbitals sigma bonds are single bonds from overlap of

o two s orbitals, o an s and a p orbital, oro two head-to-head p orbitals

pi bonds are multiple bondso sideways overlap of p orbitalso region above and below an imaginary line connecting the nuclei of the two atomso sigma bond must form first

only if unhybridized p orbitals remain on the bonded atoms occur when sp or sp2 hybridization is present on central atom

but not sp3hybridization layman’s terms

o Single bonds: A Sigma bondDouble Bonds: Sigma + Pi bondTriple Bonds: Sigma + 2Pi bonds

States of matter Gases, including the kinetic molecular theory, gas law relationships, molar

volumes, density, and stoichiometryKinetic Molecular Theory

Experimentally explains the gas laws1. A gas consists of a collection of small particles traveling in straight-line motion and

obeying Newton's Laws.2. The molecules in a gas occupy no volume (that is, they are points).3. Collisions between molecules are perfectly elastic (that is, no energy is gained or lost

during the collision).4. There are no attractive or repulsive forces between the molecules.5. The average kinetic energy of a molecule is 3kT/2. (T is the absolute temperature and k is

the Boltzmann constant.)Gas Laws

STP corresponds to 273 K (0° Celsius) and 1 atm pressure. Memorize conversion units.

o 1 atm = 760 /mmHg = 101,325 pascals Combined Gas Law

o  P1V 1

T 1  = 

P2V 2

T 2

Boyle’s Law (Boil on top)o P1V1 = P2V2

Gay-Lussac’s Law (Gay = Left earring= left politics = liberal)

o  P1

T1  = 

P2

T 2

Charles’ Law (the remaining law)

o  V 1

T 1  = 

V 2

T 2

Ideal Gas Lawo PV=nrto PV = gRT / FWo FW = gRT / PV

FW = formula weight g = weight

Van der Waals equation for n moles of gas

o

Dalton's Law of Partial Pressures o states that the total pressure of a mixture of nonreacting gases is the sum of their

individual partial pressures

o Ptotal = Pa + Pb + Pc + ...oro Ptotal = naRT / V + nbRT / V + ncRT / V + ... oro Ptotal = (na+ nb+ nc+ ... )RT / V

Molarity vs Molality vs Densityo Molarity = moles of solute / liter of solution ( M = n / V)o Molality = moles of solute / kg of solvent ( m = n / kg)o Density = mass of solution / volume of solution ( d = mass/V)

Liquids and Solids, including intermolecular forces in liquids and solids, types of solids, phase changes, and phase diagrams

Solutions, including molarity and percent by mass concentrations, solution preparation and stoichiometry, factors affecting solubility of solids, liquids, and gases, qualitative aspects of colligative properties

Forces, Solids, and Liquids Strongest intramolecular forces (hold one molecule together) in order

o Covalent network o Ionic bondingo Metallic bonding

Solid classeso Molecular

Relatively low melting and boiling points; brittle pureo Network

Hard, rigid, brittle; very high melting points; insoluble in watero Metallic

Malleable, ductile, lustrous, electrically and thermally conductingo Ionic

Hard, rigid, brittle; high melting and boiling points; those soluble in water give conducting solutions

o Atomic Made of only 1 type of element; physical characteristics vary dramatically;

can be used in conjunction with other class ex: H2 atomic molecular solid Liquid

o kinetic energy of the molecules can partly overcome the intermolecular forces, allowing the molecules to move past one another

Intermolecular forces in liquids and solids Intermolecular forces are the responsible for different phases (connect

individual molecules) In Liquids, Listed strongest to weakest

o Hydrogen bonding H to a N, O, or F Unshielded H proton bonds to lone pair on N, O, or F

o Dipole-dipole Attraction due to dipole moments with neighbors Happen to all polar molecules

o London Dispersion Forces From instantaneous neighboring electrical attraction Happens to all molecules Strength depends on polarizability

Larger molecules with many electrons tend to be more polarizable the London interactions play larger role for big molecules than small ones.

Depends on shape Longer molecule = more sites for bonding

Boiling point / Freezing point / Viscosity / Surface Tension / Vapor Pressure

o Viscosity Resistance to flow

o Surface Tension Tendency of the surface of a liquid to be pulled inward, resulting in a

smooth surface.o Vapor Pressure

pressure exerted by the vapor of a liquid or solid when the vapor and the liquid or solid are in dynamic equilibrium

o Stronger intermolecular bonding = higher boiling point higher freezing point higher viscosity higher surface tension lower vapor pressure

In Solidso Amorphous Solid

A solid in which the atoms, ions, or molecules lie in a random jumble with no long-range order.

glass and buttero Crystalline Solid

A solid in which the atoms, ions, or molecules lie in an orderly array. NaCl, diamond, and graphite

o Molecular Solids molecules held in place by intermolecular forces

o Amorphous Molecular Solid (Weak Intermolecular Forces) Very soft Examples: Paraffin wax, which is a mixture of long-chain hydrocarbons

that lie together in a disorderly way because the forces between them are so weak

o Crystalline Molecular Solids (Strong Intermolecular Forces) Hard Brittle Sucrose molecules C12H22O11 are held together by hydrogen bonding

between their numerous –OH groups

Phase Change/ Phase Diagram

Factors Affecting Solubility Of Solids, Liquids, And Gases, Common-Ion Effect

o Decreased solubility if ion of a salt is already present in the equalized solution Use le chatlier

o More ion is added to a solution at equilibrium… Temp

o Solid Heat + solid on reactants

Add heat shifts to products --- more solubility Heat + dissociated ions on product

Add heat shifts to reactants --- less solubilityo Liq

No liq liq solubility caseso Gas

Dissolving gas in liquid is exothermic (gas loses heat in the liq to the product)

Inc temp= less solubility Pressure

o Negligible for solid+liqo Gas

Henry’s Law When temp is constant, solubility corresponds to partial pressure P= kh * C

o Kh is Henry constant Partial Pressure decreases, Concentration of gas in liquid

decreases, Solubility decreases

Qualitative Aspects Of Colligative Properties

Add more solute,

1. Relative lowering of vapor pressure2. Elevation of boiling point3. Depression of freezing point4. Osmotic pressure.