Chemistry Exam 2 Test Answers – Flashcards

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Ionic Compound Characteristics
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not malleable

high melting/boiling point

don't conduct electricity except when dissolved (free ions)

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Covalent Compound Characteristics
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stronger than ionic

don't conduct electricity

low melting/boiling point

not solid at room temp

distinct molecules

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Atomic Radius Trends

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increases going down a group

decreases from L--> R

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Atomic Radius Exceptions
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Ga < Al

Ga has higher Zeff

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Ionization Energy Trends
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increases left to right

decreases going down a group

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Ionization Energy Exceptions
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B<Be and Al<Mg

N>O, P>S, As>Se

 

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How to find group number through IE
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count number of IEs before HUGE JUMP in value

that equals valence e-

that equals group number

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Electron Affinity
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amount of energy to add e-

positive or negative

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when gain e-, EA is
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negative
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when lose e-, EA is
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positive
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Electron Affinity Trends
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Halogens: -(favorable)EA

Noble gases: +(unfavorable)EA

C has -EA

N has +EA

 

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trend in gaining or losing e-

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McNa
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oxide
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binary compound with oxygen
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metal oxide in water
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basic
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nonmetal oxide
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acidic in water
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Trends In Ions
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Anions: radius increase, IE decrease

Cations: radius decrease, IE increase

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Isoelectronic series
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series of atoms and ions with exact same number total e-

can only have 1 neutral atom

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Add 1st e- = -EA
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exothermic
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Add 2nd e- = +EA
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endothermic
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Ionic bonds
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transfer e-

metals and nonmetals

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covalent bonds
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share e-

nonmetals

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metallic bonds
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pooling of e-

metals

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duet rule
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H, He, Li, Be
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electrostatic attractions
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cation and anion
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ionic compounds must be        in terms of charge
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neutral
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electrostatic energy equation

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Electrostatic energy = (charge cation)(charge anion) = ∆H˚lattice                  (cation radius)+(anion radius)
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lattic energy trends

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ion size increases, lattice energy decreases

ion charge increase, lattice energy increases

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charge is a bigger influence than radius
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diatomic molecules
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H2, N2, O2, Halogens
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Hess's Law
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change in energy depends on start and end, not path
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How do you find the highest lattice energy when comparing compounds?
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highest charge

smallest radius

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bond energy
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energy needed to break a covalent bond
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bonds strength and bond energy
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strong bond = high BE

weak bond = low BE

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breaking bonds gives off energy
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A ; B(g) ; A(g) + B(g)∆H˚bond breaking ;= BEAB;;;;;;;;;; always; 0
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making bonds takes energy
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A(g) + B(g) ; A ; B(g)∆H˚bond formation ;= -BEAB;;;;;;; always; 0
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bond length
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how close we can get the nuclei

sum of the covalent radii

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bond order
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what type of bond we have
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bond length and bond strength
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A;B
Bond orderBond lengthBond strength
Single Longest Weakest
Double ;

;

Triple ShortestStrongest
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energies in molecules
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bond: leads to energy of reactions (PE)

translational: moving around in space (KE)

rotational: spin (KE)

vibrational: bond wiggling (KE)

each molecule has all at once, all the KEs

;move all KE at same temp, bond energy leads to energy changes in reaction

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melting points and boiling points break...

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lattice interactions

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why do ionic compounds have high melting and boiling points?
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the melting and boiling points do not affect covalent bonds
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what is an exception to covalent bonds and low melting/boiling point?
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diamond is a very hard network of carbons

hard substance

high melting point

covalently bonded

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change in energy equation
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∆E = Ein- Eout
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electronegativity

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measurement of an atom's tendency to pull on e- in a bond
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EN trends

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increases towards F

EN for H=P

B<H<C

F is the highest at 4.0

 

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polar covalent
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∆EN > 0

bonds between two different nonmetals

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nonpolar covalent
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∆EN = 0

bond between two atoms of the same nonmetal

H-P bond nonpolar

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ionic character goes up as ΔEN increases
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                 H-P      H-C     H-N      H-O      H-F      

   ---------------------------→

  -------------------------→

 

 

∆EN     ioniccharacter
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greater EN value
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greater pull on e-
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greater the difference between the ENs
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greater the ionic character
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EN trend
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increases L-->R

decreases down a group

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Metalllic Bond Characteristics
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no set # of atoms in a metal sample

metals deform instead of shatter--malleable

conducts electricity and heat (solid and liquid state)

most are solids

moderate-high melting point

much higher boiling point

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ammonium

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NH4+
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hydronium
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H3O+
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acetate
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CH3COO-

(C2H3O2-)

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cyanide
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CN-
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hydroxide
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OH-
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hypochlorite
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ClO-
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chlorite
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ClO2-
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chlorate
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ClO3-
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perchlorate

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ClO4-

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nitrite
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NO2-
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nitrate

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NO3-
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permanganate
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MnO4-
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carbonate
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CO32-
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hydrogen carbonate

(bicarbonate)

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HCO3-
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chromate
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CrO42-
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dichromate
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Cr2O72-
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peroxide
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O22-
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hydrogen phosphate
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HPO42-
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dihydrogen phosphate
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H2PO4-
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sulfite
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SO32-
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sulfate
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SO42-
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hydrogen sulfate

(bisulfate)

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HSO4-
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the ion with the most O atoms
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per        ate
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the ion with one fewer O atoms
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-ate
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the ion with two fewer O atoms
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-ite
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the ion with the least (three fewer) O atoms
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hypo        ite
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1

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mono-

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2
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di-
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3
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tri-
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4
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tetra-
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5
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penta-
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6
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hexa-
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7
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hepta-
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8
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octa-
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9

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nona-
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10
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deca-
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methane
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CH4
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ethane
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C2H6
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how do you find number of H atoms for alkanes?

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double number C atoms and add 2
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propane
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C3H8
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butane
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C4H10
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pentane
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C5H12
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hexane
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C6H14
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heptane

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octane
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C8H18
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nonane
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C9H20
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decane
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C10H22
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how do you decide which lewis structure contributes more? (think formal charge)
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want lowest magnitude of formal charge

most negative formal charge on most electronegative atom

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there is no double bond with B
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empirical formula
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relative numbers of atoms with smallest ratio possible
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molecular formula
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shows actual number of each type of atom
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structural formula
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shows how atoms are connected
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molecular weight
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sum of atomic masses of every atom in one molecule

g/mol

amu/molecule

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molecular mass
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mass of molecular formula
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empirical mass
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mass of empirical formula
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in ionic compound, molecular mass=empirical mass
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Ionic Nomenclature--Main Group Metals
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Give name of metal (cation)

Name of nonmetal with -ide suffix

 

Ex: LiBr --Lithium Bromide

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Ionic Nomenclature--Transition Metals

 

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Give name of metal (cation)

Add charge in parentheses and in roman numerals

Add name of nonmetal with -ide suffix (anion)

 

Ex: FeCl3--Iron (III) chloride

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Polyatomic Ion Nomenclature
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Use name

No suffixes

 

Ex: NaNO3--Sodium nitrate

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oxyanions
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anions containing oxygen
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MgSO4 • 7H2O
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the molecule is hydrated
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Covalent Nomenclature--Binary Compounds
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Name of 1st element--lower group number, or higher period number (H is never first)

Name 2nd element with -ide suffix (O with hallogen, name hallogen 1st)

Indicate number of atoms with prefix (never used mono- with 1st element)

 

Ex: P2Cl5-- diphosphorous pentachloride

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Binary Compounds--Common Names
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H2O: water

NH3: ammonia

CnH2n+2: alkane

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How to draw Lewis structures
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Place elements relative to each other (pick central atom--lowest group # or highest period #, noble gas)

Count valence e-

Add single bonds between central atoms and terminal atoms

Calculate bonding pairs

Fill out octets with lone pairs

Count valence e- used (if equals # valence e-, then we're done)

;

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number bonding pairs equation
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[8(# atoms)-# valence e-]/2
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resonance structure
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actual structure = average of all resonance structures

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resonance
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involves placement of double and triple bonds

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bond order in resonance
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(bonding pairs)/(bonds)

;

;

Ex:O3=3/2

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delocalized e-
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e- not stuck in between two atoms, free to roam across molecule

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formal charge equation
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count bonding pairs as 1

lone pairs separately

decide charge if more or less than number valence e-

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Exceptions to Octet Rule
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not enough e- (Be or B)

odd number e- (at the end, take away from least electronegative element--NO2 is weird)

too many e- (expand octets--in row 3 or lower, extra e- on central atom)

 

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puttting (+) formal charge on something very electronegative is bad
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table showing usual bonding and lone pairs for C, N, O, Halogens, and H
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AtomsBonding pairsLone pairs
C40
N31
O22
Halogens13
H10
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molecular geometry
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arrangement of e- groups around central atom
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e- group
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bond or lone pair each count as one

 

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molecular shape
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dependent on atoms (terminal) around central atoms

where the atoms can be based on number of e- groups

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VSEPR
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valence shell e- pair repulsion

e- groups arrange themselves around atoms to maximize distance between them

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angles in geometry
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linear: 180°

trigonal planar: 120°

trigonal bipyramid: 90°, 120°, 180°

(t-shaped: 90°, 180°

linear: 180°)

octahedral: 90°, 180°

 

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geometry=shape
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when all e- are bonding groups
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A: central atom

X: terminal atom

E: lone pair

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only count lone pairs on central atom

 

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with two central atoms, talk about shape/geometry separately for central atoms
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to make polar molecule
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break symmetry using lone pairs or changing the identity of terminal atoms
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isomer
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two different molecules with the same formular
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P less electronegative than N, P=H
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need polar bonds before you can have polar molecule
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to determine number of e- groups
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(bonds + lone pairs) around central atom
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hybrid orbital formation
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start with an s orbital

need as many hybrid orbitals as e- groups

end with as many hybrid orbitals as starting atoms

mix in p orbitals to get proper number

add d orbitals when necessary

form σ bonds or hold lone pairs

π bonds with unhybridized p orbitals

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σ bond
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head-to-head overlap of hybrid orbitals

first bond between any 2 atoms

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what dictates hybridization?
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geometry and shape
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π bonds
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side-to-side overlap of unhybridized p orbitals

any multiple bonds

cannot be rotate

each p orbital can only form 1 π bond, not 2

 

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how many σ bonds and π bonds in a single bond?

double bond?

triple bond?

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1 σ, 0 π

1 σ, 1 π

1 σ, 2 π

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