Honors Chemistry Mid-Term Study Guide: Concepts to Know

Topic #1.) What is Chemistry?Chemistry- the study of the composition of matter and the changes it undergoesMatter- has mass, takes up spaceMass- a measure of the amount of matter in a sample

Topic #2.) Metric System Topic#3.) Factor-label Method for Unit ConversionTetra T Tm 1Tm=10^12m Giga G Gm 1Gm=10^9m 1. 34.83cm^3 = _______pLMega M Mm 1Mm=10^6mKilo k km 1km=1000mHecto h hm 1hm=100mDeka da dam 1dam=10m ----- --- m 1m=1m 2. 9.80 m/s^2 = _______ km/day^2Deci d dm 1m=10dm Centi c cm 1m=100cmMilli m mm 1m=1000mmMicro m m 1m=10^6mmNano n nm 1m=10^9nmPico p pm 1m=10^12pm A) 3.483*10^10 pL; 7.32*10^5 km/day^2Converting Between “Meter-based Volume” and “Liter-based volume”1cm^3 = 1mL 1dm^3 = 1L 1m^3 = 1000L

Topic #4.) Significant figures, Accuracy, PrecisionSignificant Figures- used to express the degree of accuracy (or uncertainty) in a number or measurement Accuracy - how close a result is to a previously agreed upon valuePrecision - how close a set of measurements are to each other (reproducibility)

Exact If The Digit is / Is it Significant? -Zero 1. 1,2,3,4,5,6,7,8,9 | Always-Counting Numbers (small) 2. Zero(s) between significant figures | Always-Metric Prefixes 3. Zeroes to the left of the first non- |-2.54cm = 1 inch zero digit | Never-12in = 1 ft, 3ft = 1yd, 5280ft = 1 mile 4. Zeroes to the right of the decimal Point at the end of the number | AlwaysRounding End of the Number:To round a number to “n” significant figures: Zeroes to the left of the decimal | Yes if decimal included -> Go to the nth digit, and look at the digit one place to the right point at the end of the number | No if decimal omitted A) If this digit is 5,6,7,8 or 9, round nth digit up by 1 B) Otherwise round nth digit as is.

Addition and Subtraction of Significant Figures Multiplication of Significant FiguresThe sum or difference is rounded to the same decimal The product (or quotient) is rounded to the same number Place as the number with the largest uncertainty. Of significant figures of the term with the fewest significant(example: uncertainty in the highest decimal place) figures.

Topic #5.) Density CalculationsDensity- the ratio of mass to volume or mass divided by volumeDensity Formula: Density = mass / volume (Think of a heart!)Density can be used as one property to help identify a substance. Example: If a mixture of oil and water was in a beaker, since the oil is more dense than water, you would see the layer of oil and the layer of water floating on it.

Topic #6.) Mole Calculations for Elements and CompoundsMole - the mount of substance that contains as many particles as there are atoms in exactly 12g of carbon-12; counting unit

Molar Mass- the mass of one mole of a pure substanceMole Ratio- a conversion factor that relates the amounts in moles of any two substances involved in a chemical reactionAverage Atomic Mass located on the periodic table. (Weighted average)1 atomic mass unit (amu) = 1.6605 * 10^-24 gramsAvogadro’s number- the number of particles in exactly one mole of a pure substanceAvogadro’s number = 6.022*10^23 particles (atoms; molecules; formula units) = 1 mol (mole)To find the mass of a molecule:The sum of the average atomic mass for each element of the molecule.Example: SO3 = 1(32.07amu) + 3(16.00amu) = 80.07amu

1. 2.25 mol of Fe = ________g of Fe

2. 16.3 mol of Ni = _________g of Ni

3. 5.00g of Ca = _______mol of Ca

4. 3.60*10^-10 of Au = ________mol of Au

5. 2,500 atoms of Sn = ________ mol of Sn

6. 7.5*10^15 atoms of Ni = ________g of Ni

A) 126g Fe; 957g Ni; 0.125mol Ca; 1.83*10^-12mol Au; 4.2*10^-21mol Sn; 7.3*10^-7g NiTopic #7.) Physical/Chemical Properties and ChangesPhysical Property- a property that can be measured or observed without changing the composition of the substance

Examples (*=ones that maintain constant):- color* -magnets* -length -area -volume -density* -temperature* -conductivity* -malleability* -freezing point*-mass -luminosity* -texture* -potential energy -heat energy -weight

Chemical Property- a property that must be determined by altering the chemical composition of a substancePhysical Changes- a change that does not alter the chemical composition of a substanceChemical Changes- a change that alters the composition of the substanceEvidence: bubbles (gas evolved), color change, release/absorption of energy, odor change, precipitate (insoluble solid)

Topic #8.) Intensive and Extensive Physical PropertiesIntensive Physical Property- property is independent of size (example: color)Extensive Physical Property- property that depends on the size of the sample (example: weight)

Topic #9.) Qualitative and Quantitative TestsQualitative Test- a description of the physical characteristics of somethingQuantitative Test- any measurement or description involving numbers

Topic #10.) Classification of Matter(Don’t forget to ask whether the boundaries are visible or not!)1. Determine if the matter is a Pure Substance or a MixturePure Substance- can’t be broken down by physical means, constant composition

Mixture- can be broken down by physical means, variable composition

2. If it is a Pure Substance, then determine whether it is an Element or CompoundElement- can’t be broken down by chemical means, only one type of atomCompound- can be broken down by chemical means, more than one type of atom, one type of particle (molecule)

2. If it is a Mixture, and the boundaries are not visible, then it is a homogeneous mixture.Homogeneous Mixture (solution)- appears uniform, no visible boundaries between components

If the boundaries are visible, then it is a heterogeneous mixture.Heterogeneous Mixture- visible boundaries, does not appear uniform

Topic #11.) Separation Techniques for Mixtures If every item is to be recovered, then must all be physical changes.-Evaporation -Magnetism -Filtration -“Skimming” -Visual Separation (“picking out by hand”) -Boiling-Distillation (separates liquids by boiling point)

Give directions for the complete separation of the following mixture: sand, iron power, copper wire, sawdust, water, charcoal and salt. All must be recovered.

Topic #12.) Structure of the AtomIsotopes- atoms of the same element with different numbers of neutrons

How two isotopes of an element are:Similar Different

-atomic number -atomic mass-chemical properties (mostly) -mass number-number of protons -number of neutrons-number of electrons in a neutral atom -stability (stable vs. radioactive)-element symbol -abundance

-half-life of radioactive isotopesIsotopic NotationName= name of element + mass number (example: “carbon-12”, “sodium-24”)Symbol

A n.c.

EZ

E=Element Symbol Atom net charge=0 (neutral)A=Mass Number n.c.> 0 (+) -> Electrons < Protons = CationZ=Atomic Number n.c. < 0 (-) -> Electrons> Protons = Anionn.c.= net charge (n.c.=#p-#e)Isotopes of Hydrogen

Symbol # of Neutrons Stable? Abundance Mass NameHydrogen 1 0 Yes >97% 1.0 amu ProtiumHydrogen 2 1 Yes <1% 2.0 amu

Deuterium (D)Hydrogen 3 2 No (radioactive) (trace) 3.0 amu Tritium (T)Topic #13.) Properties of Metals, Nonmetals and Metalloids

Metals NonmetalsPhase at Room Temperature: Solid (excluding Hg Mercury) Depends on the elementAppearance: Lustrous DullWorkability: Malleable, Ductik BrittleConducts Heat & Electricity: Yes No

Combines Chemically with: Nonmetals Metals + Nonmetals

Metalloids-Share some properties with metals and some with nonmetals-Can combine with both metals and nonmetals-Semi-Conductors (silicon base for microelectronics)

Topic #14.) Element Symbols and Compound Formulas

Topic #15.) Mass Number and Atomic NumberAtomic Number-unique for every atom (each element is defined by its atomic numberZ= number of protons in the nucleusAtomic Mass-the mass of one atom (Includes protons, neutrons and electrons), different for each isotopeAtomic Mass Unit (amu)- 1 amu=1.6605*10^-24 gramsAtomic Number- discovered by Henry Mosely (1914, UK) using x-rays

Topic #16.) Hyphen Notation for IsotopesName = Name of element + mass number (example: “carbon-12”, “sodium-24”)

Topic #17.) Atomic Theory ExperimentsJ.J. Thomson (UK) Plum Pudding Experiment

-all gasses exhibited negatively charged beam so they all have Negatively charged particles-beam was blocked by metal; electrons have mass-calculated mass/charge for electrons“Plum Pudding”:

Robert Millikan (US) Oil Drop Experiment-negative charges that floated were all multiples of -1.6*10^19 C; this must be the smallest

negativecharge (= charge on one electron)-now able to find mass of electron-charge of one electron x mass/charge = mass of one

electron

Earnest Rutherford (1911) “Gold Foil” Experiment New Zealand-low probability of alpha particles hitting a massive

source ofpositive charge-all positive charge (and most of the mass) of an atom

is localized in a small region; therefore most of the

atom is

empty spaceExpected:

Found:

Topic #18.) History of Atomic Theory and the Periodic TableDemitriy Mendeleev (1870) (Russian)-created first modern periodic table-grouped the elements with similar properties (or trends)-about 60 elements-arranged by increasing mass-left space for undiscovered elements and predicted properties

Democritus-matter is composed of tiny indivisible particles called “atoms”- “Atomus”- indivisible- “hook + key” structureAristotle-Earth, Air, Fire and Water- “Four Elements”- 5th Element “quintessence” (phlogiston)

Antoine Lavoisier (French)- “Father of Modern Chemistry”- Law of Conservation of Mass

Joseph Louis Proust (French)-Law of Definite Proportions (constant composition)

Joseph Priestley (British)-discovered and characterized oxygen

John Dalton (1800s) (British)-English school teacher who proposed an explanation for the law of conservation of mass, law of definite proportions and law of multiple proportions; reasoned that elements were composed of atoms; only whole numbers of atoms can combine to form compounds-Law of Multiple Proportions (CO2, CO1)-Determined Relative Atomic Mass (Incorrectly)John Dalton’s Atomic Theory1) All matter is composed of atoms (small particles) Still True

2) Atoms of the same element identical in size, mass Still True- atoms of different elements -> different and other properties; atoms of different elements atoms of same element have “unifying” characteristics differ in those properties No Longer True- atoms of an element can differ in mass (isotopes)

3) Atoms cannot be subdivided, created or destroyed Still True- can’t be done chemically

No Longer True- Fission/Fusion, Subatomic particles, natural radioactivity

4) Atoms of different elements combine in simple Still True- formulas use integers whole number ratios to form chemical compounds No Longer True- not always simplest ratio (1:1)

Evidence of non-stoichiometric compounds

5) In chemical reactions, atoms are combined, separated Still True or rearranged

Henry Moseley (1911)Discovered a previously unrecognized pattern in the periodic tableThe elements fit into patterns better when they were arranged in increasing order according to nuclear charge or the number of protons in the nucleusLed to the modern definition of the atomic number and the recognition that the atomic number (not atomic mass) is the basis for the organization of the periodic table.Periodic Law- The physical and chemical properties of the elements are periodic functions of their atomic numbersIn other words, when the elements are arranged in order of increasing atomic number, elements with similar properties appear at regular intervals. Topic #19.) Average Atomic Mass/Isotope AbundanceAverage Atomic Mass- weighted averageAAM= (mi x ai) = sum

= m1a1 + m2a2 + m3a3 m= mass of isotope (amu) a=decimal abundance of isotope (between 0-1)

Mystery Element - Solve AAMAn element contains 1.40% of isotopes with a mass of 203.973 amu, 24.10% with a mass of 205.9745, 52.40% with a mass of 207.9766 amu and the rest have a mass of 206.9759 amu. What is the average atomic mass and which element is it?

A: 207.2 amu; Pb (Lead)

Isotope Abundance-can only be done with two unknowns

Gallium consists of two naturally occurring isotopes with masses of 68.926 and 70.925 amu. The average atomic mass of Ga is 69.72 amu. Calculate the abundance of each isotope. (SIXTYNINE<3).

A: 69Ga: 60.3%, 71Ga: 39.7%Topic #20.) Electron Configuration for Ground-State Atoms, Excited-State Atoms, and IonsElectron Configuration-written as a series of tri-graphsElectron configuration is used for counting number of valence electrons and for predicting chemical properties.Aufbau Principle- “aufbau” -> “building up” (German)Electrons placed in the lowest energy sublevels firstOctet Rule: an atom may not have more than eight electrons in the outermost energy level (highest “n”)

Exceptions to Aufbau Principle: Cr, Cu, Mo, Ag, AuTo write the full electron configuration for exceptions, remove one electron from the highest filled shell and place in next sublevel.Example:Cr should be: 1s^2 2p^6 3p^6 3s^2 3p^6 4s^2 3d^4

But, magnetic susceptility measures show that this cannot be true.Cr : 1s^2 2p^6 3p^6 3^s2 3p^6 4s^1 3d^5

Noble-Gas Electron ConfigurationNoble Gasses: He, Ne, Ar, Kr, Xe, RnNote all have full outer shells (8 electrons, except He)All occur at the end of the rowUse [ ] to abbreviate the inner shell electronsWriting Noble Gas ConfigurationFind noble gas with the largest number of electrons less than the number of electrons in the item of interestThen write out the rest of the electron starting from the chosen noble gas.

Electron Configuration for IonsCations (+) - electrons are removed first from the highest sublevel in the highest shellExample: Na - 1s^2 2s^2 2p^6 3^1 (11 electrons)

Na+ - 1s^2 2s^2 2p^6 (10 electrons)Same electron count as Neon

Na+ is isoelectronic with Ne

Anions (-) - electrons are added to the highest sublevel within the highest energy levelNotable- H^- = 1s^2All other anions will be found on nonmetals or metalloids and will add electron to “p” sublevelExample: Br- = [Ar]4s^2 3d^10 4p^6

S- = [Ne]3s^2 3p^5

Atoms in the Excited State (* denotes excited state)Has the same number of electrons but promotes only one electronPromote the electron in the highest energy sublevel within the highest shell (n)Place the electron in the sublevel that is at least one “n” higher (Mr. B suggests “8s” sublevel)K= [Ar] 4s^1K*= [Ar] 5s^1

Topic #21.) Quantum Mechanical Model of Atom/ Bohr ModelQuantum Mechanical Model - electron has both particle and wave propertiesBohr Model (1913)- Niels Bohr used the Hydrogen atom as basis; works well for one-electron species (H, P, He+)Does not account for electron to electron repulsion in multi electron atomsElectrons travel in certain allowed paths (planetary model)

Four Quantum Numbers:1. Principal Quantum Number (n)2. Angular Momentum Quantum Number (l)3. Magnetic Quantum Number (m or ml)4. Spin Quantum Number (s or ms)

Principal Quantum NumberDenotes energy level n= 1,2,3.….Each energy level has “n” sublevelsAngular Momentum Quantum NumberFor each ‘n’ there are “n” sublevels:l=0,1,2,3.…. N-1 = non-negative integersMagnetic Quantum NumberDenotes orbital (region of probability that can be possessed by up to 2 electrons)These have “shapes” described by probability boundaries

Each sub-level l has “2l+1” orbitalsNegative and positive integers

So far, two electrons can have:The same energy levelThe same sublevelThe same orbital

But they must each have a unique set of four quantum numbers (Pauli Exclusion Principle)Spin Quantum NumberS= +½ or - ½ “Spin up” “Spin down”

Topic #22.) Aufbau Principle, Pauli Exclusion Principle, Hund’s rule, Heisenberg Uncertainty PrincipleAufbau Principle- electron is placed in the lowest energy sublevel firstPauli Exclusion Principle- No two electrons in an atom have the same set of four quantum numbersHund’s Rule- Fill empty orbitals in a sublevel and then fill the half-filled orbitalsHeisenberg Uncertainty Principle- one cannot know both the position and velocity of an electron at the same time (momentum)

Topic #23.) Shapes, Properties, and Relative Energies of Atomic OrbitalsProbability BoundariesS

Px Py Pz

Dxz Dyz Dxy

Dx^2-y^2 Dz^2

Topic #24.) Periodic Table玅Organization, Names of Areas, Sublevels Being “Filled”Group 1 - Alkali Metals Group 2 - Alkaline Earth Metals Group 3-12 - Transition Metals (“d” block)Group 13- Boron Group Group 14 - Carbon Group Group 15 - Pnictogens (“choking gases”)Group 16 - Chalcogens (“chalk formers) Group 17 - Halogens (“Salt Formers”) Group 18 - Noble Gasses Groups & Columns- VerticalPeriods & Rows- Horizontal

Topic #25.) Periodic TrendsAtomic Radius- distance from nucleus to the edge of electron cloudPeriodic Trend:Pull increases (number of protons going up)Shielding is constantElectron cloud is pulled in tighter Therefore atomic radius goes down (decreases)Group Trend:Shielding goes up/increases while Zeff goes down/decreasesElectron cloud is not as held as tightly; the cloud spreads out

Atomic radius goes up (increases)

Ionic RadiusCompare parent atom with ionCompare different ions of the same element (example: Fe2+ vs. Fe3+)Same change, same group (example: F- vs. C-, Ca2+ vs. Ba2+)Isoelectronic species have same electron configurationCations (+)- always smaller than parent, ratio of electrons to protonsGreater electron to proton ration = larger radiusExample: Na> Na+; 11 electrons : 11 protons > 10 electrons : 11 protonsNa has less pull per electron, Na+ has less shieldingAnions (-)Also uses ratio of electrons to protonsMost Anions are larger than most CationsIsoelectronic SpeciesStill use ratio of electrons to protons

First Ionization Energy (1 st IE) Always described by the following equation:

X(g)X+(g) + e- (x)= elementDefined as the energy required to remove the first valence electronAlways EndothermicAlways describes formation of +1 ion even if it isn’t favorableAs ionization energy increases, it becomes more difficult to remove electronsPeriodic TrendPull goes up (increases); shielding constantElectrons are held more tightlyIonization energy goes up (increases)Group TrendShielding goes up (increases)Zeff goes down (decreases)Gets easier to remove electron because it’s not held as tightlyIn relation to the periodic table:

Electronegativity (“electron grabbiness”)Electronegativity represents the degree of attraction between the nucleus of the atom and the electron cloud of a neighboring atomElements with higher electronegativity tend to gain electrons when they reactElectron “GPA”; scale from 0.0 to 4.0; highest is Fluorine (4.0); F>O>NElements with high electro negativity tend to form ANIONS when they reactNoble gases are not given electro negativity values because they do not reactPeriodic TrendPull goes up (increases); shielding constantZeff goes up (increases)Results in more pull on the electron cloud of neighboring atomsGroup TrendShielding goes up (increases) but Zeff goes down (decreases)Less able to attract neighboring electronsIn relation to the periodic table:

Electron Affinity (EA)The energy required to add an electron to an atom in gas phase

X(g) + electron X-(g)Not the reverse of Ionization Energy

Group trend is erraticElectron Affinity is stronger (more favorable) for nonmetals vs. metals (more likely to gain an electron and form anion)Periodic Trend As you go right, Electron Affinity gets stronger(Non-metals have a stronger affinity for adding electrons)Non-metals tend to form anions when they reactEnergy gets more negative (exothermic/releases energy)ReactivityTwo trends: one for metals, one for nonmetals

Topic #26.) Nuclear Pull, Nuclear Shielding, Effective Nuclear Charge, and Their Relationship to Periodic TablesAtomic Radius, First Ionization Energy, Electronegativity, Electron Affinity, Reactivity, Metallic CharacterPeriodicityNuclear Pull- relates to the number of protons (+ charge in the nucleus)Nucleus “pulls” on (attracts) electrons; more protons = more pullAtomic number goes up, protons goes up, pull goes upMore important (influential) in periodic trends (since number of inner-shell electrons is roughly constant)In relation to the periodic table:

Nuclear Shielding- relates to the number of inner shell electrons (filled shells)Shielding is roughly constant across a rowShielding increases dramatically down a columnIn relation to the periodic table:

Zeff = Z - SZ = atomic number (or nuclear charge) S= shielding constant Zeff= effective nuclear charge (charge or pull felt by outer shell electrons)

Topic #27.) Writing Names and Formulas for Ionic Compounds (Binary, Transition Metals, Polyatomic Ions)Formula for Binary Ionic Compounds

Def- two elementsOne metallic element (Cation)One non-metallic element (Anion)

Rules: 1. Cation always written first 2. Mole ratios are in simplest terms 3. Omit “1” as subscriptCross & Drop Method (I’m not going to explain that.)Name Monovalent ElementsOnly form one oxidation number (change in compound)Multivalent ElementsRemaining metals in the “p”, “d”, “f” block

>1 oxidation stateName according to chargeExample: Fe2+ Iron (II) Ion

Sn2+ Tin (II) IonAnion NamesName= Truncated Name of Element + ideExample: Cl- Chloride

O2- Oxide

Polyatomic Ions-group of atoms bonded together with a single overall chargeStill cross and dropNaming OxyanionsX= Cr, As, P, S, Se (CrAsPSSe) X= othersN/A XO^n- Hypo____iteHypo___ite XO2^n- ____ite____ite XO3^n- ____ate_____ate XO4^n- per___ate

All elements with same “X” have “same ‘n’”

Charge on Oxyanions Based on X, charge on Xom^n- (n-) is the same as the charge on x when x combines with a metalGroup 17 -1 Group 16 -2Anions with “H”Add “Hydrogen” to the nameHS- = Hydrogen Sulfide IonH2PO4 = Dihydrogen Phosphate IonTopic #28.) Writing Names and Formulas for Binary Molecular CompoundsIn a molecular compound, there is no cation or anion. The element farthest away from fluorine (F) is written first.

AxByA + B are nonmetals and A is not equal to H Greek Prefix for “x” if x>1 then name of the element A

Grek preix for X if X>1 + Name of Element A Greek Prefix for Y + “ide” name of B

1 = mono 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa7 = hepta 8= octa 9= nona 10 = deca

Topic #29.) Writing Names and Formulas for AcidsAll acids have H+ as the cation. The anion can be a polyatomic ion (like NO3-) or a single element (like Cl-).All anions have one of three possible endings: -ide -ite -ate.1) If the anion ends in “ide” then the ending is “ic”

Acid Name = “hydro” + anion name - “ide” + “ic” + acid Hydrochloric AcidThis is also true for polyatomic ions like cyanide (CN-), which would become Hydrocyanic Acid2) If the anion ends in “ite”, then the ending is “ous”

Acid Name = Anion name - “ite” + “ous” + acid Nitrous Acid3) If the anion ends in “ate” then the ending is also “ic”

Acid Name = Anion name - “ate” + “ic”+ acid Perchloric AcidTopic #30.) Writing Formulas of Alkanes, Names of the First Ten AlkanesAlkanes are hydrocarbons (binary molecular compound of carbon + hydrogen)Alkanes have the formula:

CnH2n+2N Form Name1 CH4 Methane2 C2H6 Ethane3 C3H8 Propane4 C4H10 Butane5 C5H12 Pentane6 C6H14 Hexane7 C7H16 Heptane8 C8H18 Octane9 C9H20 Nonane10 C10H22 Decane

Topic #31.) Names and Formulas for Hydrates 玅 Determining Formulas From Experimental DataHydrates are compounds that attract and bond with water molecules when they crystallize. The two parts of the hydrate are the anhydrous salt and the water of hydration. The ratio of the water molecules is always a whole number. To name a hydrate: (CUSO4 * 5H2O)1) First name the salt. (Copper (II) Sulfate)

2) Determine the prefix to be used based on the number of water molecules. (Copper (II) sulfate penta-)3) Add the word “hydrate” to the end of the prefix. (Copper (II) Sulfate Pentahydrate)

Prefix Moles of Water Name FormulaMono- 1 Monohydrate XY*H2ODi- 2 Dihydrate XY*2H2OTri- 3 Trihydrate XY*3H2OTetra- 4 Tetrahydrate XY*4H2OPenta- 5 Pentahydrate XY*5H2OHexa- 6 Hexahydrate XY*6H2OHepta- 7 Heptahydrate XY*7H2OOcta- 8 Octahydrate XY*8H2ONona- 9 Nonahydrate XY*9H2ODeca- 10 Decahydrate XY*10H2O