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Quantum Theory - This theory replace Bohr because his nergy levels only worked for hydrogen -The quantum theory uses complex mathematical equations to decrible waves - The model predicts quantized energy levels of electrons. It depends on the probility of finding an electrons in a certain position -This is categorized the 7 energy levels into 4 orbits Orbitals - An area where an electron can be found - There are 4 orbitals; s,p,d, f - The orbitals are filled based on the location of the electrons on the periodic tables S-Orbitals - Given a 3-d figure, the s-orbital would look like a sphere - It can hold a max of 2 electrons-one pair of electrons - S-orbitals will occur in all 7 energy levels P-orbitals - Electrons begin filling the p-orbitals in the 2nd energy level after filling the 2s-orbital - It can hold a total of 6 electron-3 electron pairs - The shape of each of the p-orbitals look like a dumbbell D-orbitals - The electrons begin filling the d-orbitals in the 3rd energy level,after filling the 4s orbital -The orbitals will hold 10 electrons-5 electron pairs - The 3-d shape of the d-orbital is a 4 x-shapes with a life-saver around the center F-orbitals - They occur in the 4th energy level after filling the 6s orbital - The f-orbitals can hold 14 electrons- 7 electron pairs - The electrons are in such chaos that there is no set shape to describe them Electron Configurations -A visual way to write how the electrons fill the orbitals. -The orbitals fill as you flow left-right and top to bottom on the periodic table:1s,2s, -Example with directions -Find out how many electrons are in the Manganese. 25 electrons - Flow left --> right and top --> bottom filling the orbitals: - 1s,2s,2p, -Self-check- add all of the superscripts; that total should match the number of electrons Practice: Write the electron configuration 1. Electron configuration of nitrogen answer: 1s^2,2s^2,2p^3 2. Electron configuration of Bromine(Br) answer:1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^5 3. Cerium (Ce)

Use of the Bohr Model While Bohr's model only worked for the hydrogen atom, his energy ideas are still used today

Electrons are in the energy levels and can move energy levels when the electrons become energized (quantized)

Energy levels of an atom

Bohr proposed the electrons can only reside in an energy level The lowest level is closest to the nucleus __Ground State__- When electrons are in the lowest possible level __Quantum__- amount of energy needed to jump energy levels (particular energies given) __Excited State__- when an electron has been quantized(given particular energy)- leads to waves of light

Calculations E=hc/ l, v=c/ l

E=energy (eV) or (Joules)

h=6.63 x 10-34 joules/hertz

c=3.0 x 108 m/s

v= frequency (Hz = 1/sec)

Trends of the Periodic Table When studying the periodic table one can tell many things about an element just by its location.These trends help scientists idenify new elements and understand why an element has different properties.

Atomic Radius - Atomic radius within a group increases as one moves vertically down the periodic table -Atomic radius within the period decreases as one moves horizontally right across the periodic table

Ionization Energy (the energy required to remove an electron from an element) - The energy required for elements within a group **decreases** as one moves **vertically down** the periodic table - The energy required for elements within a period **increases** as one moves **horizontally right** across the periodic table

Shielding Effect -A decrease in the attraction of the outer electrons (valence electrons) to the positively-charged nucleus - **Increases** as one moves **vertically down** the periodic table - It remains **constant** as you move **right** across the periodic table because the electrons aren't being added to a new energy level

Electronegativity (EN) - How strong the bonds are within the compound - **Decreases** as you move down the periodic able because the energy levels are growing - **Increases** as you move right across the periodic a table because more p+ are added to the nucleus allowing for more electrons F is the most electronegative element at 4.0 and Francium is the least at 0.7 (Noble gases are excluded)

Wlectron affinity - A measure of the energy change that occurs as an electron is added to an atom - Has the same trends as electronegativity for the same reasons (Last Slide)

Atomic Mass Number(Mass Number) The average of alll of the masses of the naturally occurring isotopes of an element

The mass number is the rounded atomic mass. It is the number of protons and neutrons found in an atom

Atomic mass is expressed in Atomic Mass Units(amu) - The mass numberis the mass of both the protons and the neutrons, nt the total mass - Scientist developed a unit to compare all atoms - 1 amu=1.66 x 10^-24 g (1/12th the mass of the carbon-12)

Average Atomic Mass on the PT -When you read the mass on the PT, the unit are amu - Cu= 63.55 amu - These average atomic masses are the average of the atomic masses of the isotopes occurring in nature - Amu when single atom; grams when larger amounts of materials

How to calculate the amu - Scientist use the % of the existence of an isotopes multiplied by the mass of all totaled to get th mass ex) Cu-exists 69.17% of the time yielding a mass of 62.94 amu and Cu- 65 exists the other 30.38% of the time with a mass of 64.93 amu. Together hey create the amu of Cu. (.6917 x 62.94 amu) + (.3083 x 64.93 amu) =63.55 amu

Conversion Factors - Avagadro's Number: __6.022 x 10^23 atoms/molecules__ 1mole - Molar Mass: __Atomic mass(g)__ 1mole

Valence electrons : # in the s+p orbitals in that period, skip d/f orbitals: same group of elements have the same # of valence electrons; group # = valence electrons ; max of 8 electrons(v); Hydrogen and Helium are exception to Octet (only total 2)

Ion- an element that has donated or taken electrons

Cations- left hand side Groups I,II,III sometimes (IV) gives away electrons Ca+2: Calcium ion

Anions- Right hand side of periodic table sometimes(IV) Groups V,VI,VIII taking in electrons O-2: oxide ion

Ionic Bonds -Oppositely charged ions attract and bond to eacg other. The compounds become know as salts. - Ex: Te attraction of a Na +1 ion to a Cl ion forms the compound commonly know as table salt Writing Ionic Formulas - Write the cation and anion from the name: Lithium oxide: Li+1 O-2 - Switch the charges to become subscripts: Li -Reduce if like charges or common multiples (+2,-2 becomes 1:1, +4,-2 becomes 2:1)

Percent Composition - Calculating the percent that an element eists within a compound - Essentially you are giving each element a grade on its participation within the compound Samples 1. Mass of elements a. H: 2*1.01= 2.02 g b. O: 1*15.99= 15.99 g
 * Determining formulas mathematically**

2. Mass of compounds 2.02 + 15.99 = 18.01 g

3a. Percent H: 202/18.01 = .112*100= 11.2 %

3b. Percent O: 15.99/ Calculating the % of an element - If we recover 12.31 g after distillation, how many g of O are present?

Working from % to formula - We can also work backwards to determine the formula of a compound. This is called the __empirical formula__. It gives the lowest whole-number ratio Step by step -When given a problem assume that you have 100 h total( like %, make it easy)25.4%=25.4 g -Calculate the moles of each element -Divide the moles of each element by the smallest mole number to get the ratio.(Round to the nearest .5) -Multiply ratio by 2 if you have a .5 ratio - Write the formula using the whole number ratio Sample A cmpd is analzd and found to contain 25.9 % N and 74.1 % O.What is the empirical formula? 25.9g N x (1molN/14.0 g)=1.85 mol N 74.1 g O x (1mol/ 15.99 g) = 4.63 mol O Ratio: 1.85/1.85 : 4.63/1.85 = 1:2.5 Whole Number: 2(1:2.5)= 2.5 Formula N2O5

Hydrates - Compuonds that have have water trapped in them - The water is trapped during a cooling process - Formula: CuSO^4 * 5H^2 0 - Naming: Copper II sulfate pentahydrate

% composition of h20 -You find the total atomic mass of the compond( all of the elements and water) - Take the mass of the water/total mass x 100% sample - BaCl2 x 2H20 -Ba: 137.3 g - Cl: 2 x 35.45 = 70.90 g - H2O: 2 x 18.01= 36.02 g - Total: 244.2 g - % H20= (36.02/244.2)x 100= 14.75%

Empirical Formula w/ hydrates - treat the compound as one thing and water as another - Complete the same step by step problems as before - Grams-->moles-->mole:mole ratio-->formula answer

Sample 10.407 g of hydrated barium iodide is heated and .877 g of H2O is driven off. Assuming this is all of the water, what is it's formula and name?

.877gH2Ox(1molH2O/18.01g)= .0493molH2O 10.407-.877= 9.53gBal2 9.53gBal2 x(1mol/391.12g)= .0244mol .244/.244=1: .0493/.0244=2 Bal2 x 2H2O Barium Iodide Dihydrate

Naming Covalent bonds 1) Elements are listed by lower group first 2) If both elements ar in the same group, the lower atomic number element is the first of the bond 3) 2nd element will end with -ide 4) Prefixes are used to tell how many atoms are in the bond(mono, bi, tri, etc) 5) first element will only have a prefix if it is more than one

Examples

BF3- Boron trifluoride Dinitrogen pentaoxide-N2O5

Chemical Reactions -Chemical reactions occur when bonds between the outermost part of the atoms are formed or broken - Chemical reactions involve changes in matter, the mking of new materials with new properties, and energy changes - Symbols represents elements, formulas describe compounds, chemical equations describe a chemical reaction Chemical equations Their job: Depict the kind of reactants and products and their relative amounts in a reaction 4 Al + 02 =Al2 O3 The numbers in the front are called stoichiometric coefficients The letters s,g, and l are the physical sates of the compounds Parts of the Reaction Equation - A= sign separtes molecules on the same side - The arrow is read as yields - Example C+ O -> CO2 - This reads " carbon plus oxygen reacts to yield carbon dioxide" Why? - Because of the principle of the conservation of matter, an equation musr be balanced - It must have the same number of atoms of the same kind on both sides Symbols -Solid(s) - Liquid(l) - Gas(g) - Aqueous sloution(aq) - Catalyst - Escaping gas(^) - change of temperature(triangle) Balancing Equations - When balancing a chemical reaction you may add coefficients in front of the compounds to balance the reaction, but you may NOT change the subscript - Changing the subscripts changes the compound. Subscripts are determined by the valence electrons( charges for ionic or sharing for covalent) Steps to Balancing Equations 1) Write the correct formula for the reactants and the products 2) Find the number of atoms for each element on the left side. Compare those against the number of the atoms of the same elment on the right side 3) Determine where to place coefficients in front of formulas so that the left side has the same number of atoms as the right side for EACH each element in order to balance equation 4) Check your answer to see if: - the number of atoms on both sides of the equation are now balanced - the coefficients are in the lowest possible whole ratios. (reduced) Some Suggestions to help you - Take one element at a time, working left to right except for H and O. Save H for next to last and O last - IF everything balances except for O and there is no way to balance O with a whole number, double all the coefficients and try again. (because O is diatomic as an element) - (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units Stiochiometry Review if you have 34.1 g of CuSO4, how many moles of CuSO4 do you have? How many molecules do you have? Write in Sig Figs.

Conservation of Mass The total mass remains constant when comparing reactants and products(the two will be equal) The total mass of hydrogen and iodine will equal the mass of hydrogen iodine.

Writing Mole Ratios This uss the coefficients of a balanced equation to show the relationship between compounds. N2 (g) + 3H2 --> 2 NH3 (g) what this means: 1 mol N2: 2 mol NH3 : 3 mol H2 Mole à Mole calculations How many moles of NH3 are produced when 0.60 mol of nitrogen reacts with hydrogen? N2 + 3H2 à NH3 (g) .60 mol N2 x 2 mol NH3/ 1 mol N2

Other conversions

1) When asked for L at STP use: __22.4 L/1 mol__ 2) When given molarity (M) remember to keep the # with moles (__6 mol/L= 6M__) 3) __1 mol/6.022 x 1023__ molecules 4) Density (g/ml)

Steps 1) Balance he equation 2) Start with the given number 3) Covert to moles 4) Use the mole: mole ratio from the balanced equation 5) Covert to the required unit using one of the conversion factors

Limited and Excess Reagents

In a chemical reaction, one compound drives how long and how much a reaction can occur. __Limiting__- determines how much product can be formed __Excess__- Some left over during the reaction process

Using the information

If we have 30 pairs of shoes and 25 people, how many people can have shoes?

How to do the problem

- Convert the grams of each reactant into moles of the product - The smaller mole value tells you which starting reactant is the limiting reactant - Use the moles of the limiting reagent to calculate the amount of products

Excess Leftover

Select one product that you formed Convert that product into grams of excess reactant Subtract those grams from the starting grams = how much is leftover

Percent Yield

- Mathematical calculation of how “good” your lab results are - % yield = __actual yield__ x 100% - Theoretical yield - Actual yield- results from lab - Theoretical yield- amount predicted from calculations

Gas Laws- Unit 9

Elements that exist as gases at 25 degrees C and 1 atmosphere- H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn

Physical characteristics - Gases assume the volume and shape of their matter - Gases are the most compressible state of matter - Gases will mix evenly and completely when confined to the same container - Gases have much lower densities than liquids and solids

Pressure = __Force__ Area Units of pressure

1 pascal(Pa) = 1 N/m2 1 atm = 760 mmHg = 760 torr 1 atm = 101,325 Pa = 101.325 KPa

Boyles Law

P a 1/V

P1 x V1 = P2 x V2

Content temperature and Content amount of gas

Charles Law

As T increases V increases as well

Variation of gas volume with temperature at constant pressure

V a T V = constant x T V1/T1 = V­2/T2

Temperature **must** be in Kelvin T(K) = t( ° C) + 273.15

Ideal Gas Equation

PV= nRT

R is a the gas constant

Used when we are discussing a single gas in a non-changing environment

The conditions 0 C and 1 atm are called **standard temperature and pressure (STP**)

Experiments show that at STP, 1 mole of an ideal gas occpies 22.414 L

R = __PV= (1 atm)(22.414L)__ nT (1 mol)(273.15K)

Dalton’s law of Partial Pressures

V and T stay constant

P1 + P2 = P total

Colligative properties

-Molality (m)- mol of solute/kg solvent

Boiling point elevation

D T= T (final)- T (intial) D T(b) = bp(solution)- bp (pure solvent) D T(b) = k(b) x m Where k(b) à boiling point elevation constant D T b(solution) = D T b(solvent) + D T

Freezing point depression

D T= T final – T initial D Tf = fp pure solvent – fp solution D Tf­ = kf x m where kf à freezing point depression constant T f(solution) = Tf(solvent) = D T

Concept

The freezing point of water is lowered proportional to the number of solute species present

Why is it better to leave the anti-freeze in your cooling system

Temp. and Solubility -Conversely a gas will be less soluble at a higher temperature -This is because when gas molecules are moving faster they are able to escape from the liquid surface