CHEM Test 3

What does Valence Bond Theory show us

• how atoms share electrons when they overlap

• explains the shape using orbitals

what does VSEPR stand for

Valence Shell Electron Pair Repulsion

what can VSEPR tell us

• Predicts the 3D shape of a molecule

• ignores orbitals

How does theshape and orientation of atomic orbitals influence bond strength

what type of bond forms during the sharing of electrons

covalent bonds

what is hybridization

• process in which atomic orbitals on the same central atom mix and form new identical hybrid orbitals

what are bonded orbitals

orbitals between 2 atoms that share electrons

what are unbonded orbitals

orbitals containing electrons that are not shared

in hybridization what happens to the number of orbitals

the # of orbitals stays the same

when writing equations for orbitals in hybridization:

• what does the superscript represent in the answer

• what does the superscript represent in the question

ex) 2s + 2p → 2sp

• answer = # of orbitals

• question = name

what is the geometry for SN = 2: electron geometry and bond angle

linear; 180

what is the geometry for SN = 3: electron geometry and bond angle

Trigonal Planar; 120

what is the geometry for SN = 4: electron geometry and bond angle

Tetrahedral; 109.5

what is the geometry for SN = 5: electron geometry and bond angle

Trigonal bipyramidal; 90 and 120

what is the geometry for SN = 6: electron geometry and bond angle

octahedral; 90

SN = 2 : Hybridization?

sp

SN = 3 : Hybridization?

sp²

SN = 4 : Hybridization?

sp³

SN = 5 : Hybridization?

sp³d

SN = 6 : Hybridization?

sp³d²

How do you find the Steric Number

SN = atoms bonded to the central atom + lone pairs on the central atom

or

SN = lines + pair of dots

where double and tripple bonds = 1 line

SN 2 with 0 lone pairs: shape?

linear

SN 3 with 0 lone pairs: shape?

trigonal planar

SN 3 with 1 lone pair: shape?

bent

SN 4 with 0 lone pairs: shape?

tetrahedral

SN 4 with 1 lone pair: shape?

trigonal pyramidal

SN 4 with 2 lone pairs: shape?

bent

SN 5 with 0 lone pairs: shape?

trigonal bipyramidal

SN 5 with 1 lone pair: shape?

seesaw

SN 5 with 2 lone pairs: shape?

t-shaped

SN 5 with 3 lone pairs: shape?

linear

SN 6 with 0 lone pairs: shape?

octahedral

SN 6 with 1 lone pair: shape?

square pyramidal

SN 6 with 2 lone pairs: shape?

square planar

how many sigma and pi bonds are made from a single bond

• 1 sigma

• 0 pi

how many sigma and pi bonds are made from a double bond

• 1 sigma

• 1 pi

how many sigma and pi bonds are made from a triple bond

• 1 sigma

• 2 pi

what are intramolecular forces and what is their strength: strong or weak?

• chemical bonds inside a substance

• strong

what are intermolecular forces IMF and what is their strength: strong or weak

• attractions btw molecules or ions caused by partial charges

• weak

what are metallic bonds composed of

metal cations and delocalized valence electrons

what are delocalized valence electrons

valence electrons that are not stuck between 2 specific atoms but are spread out over three or more atoms which makes the molecule more stable

what are the requirements for ion-dipole forces

• molecules with charges that are dissolved in polar solvent → solutions only

what is hydrogen bonding

• when Hydrogen is bonded to a small electronegative atom with lone pairs

what are some bonded exceptions to hydrogen bonding

• H-S

• H-P

• H-C

• molecules with F that has no H connected to F

what are the requirements for hydrogen bonds

• Hydrogen directly bonded to N,O, or F

• a lone pair on a neighboring molecule

what are the requirements for dipole-dipole force

• polar bonds that dont cancel / polar molecule

what does a bigger dipole moment do to attraction and boiling point

• higher boiling point

• stronger attraction

what happens in a dipole

• + pole of one molecule attracts to the - pole of the next

what are the requirements for london dispersion

• all molecules have it

• only force in non polar molecules

what is london dispersion

• when electrons breifly bunch up on one side → instant dipole

what effect does surface area have on london forces

• more SA = stronger london forces

what is the relationship between IMF and boiling point

• stronger IMF = higher BP

what is the relationship between molecule size and boiling point

• bigger molecule with same IMF = higher BP

what is the relationship between hhydrogen bonds and boiling point

• more H bonds = higher BP

what is the unit of measure for surface tension

J/m²

what is the relationship between IMF and surface tension

• stronger IMF = higher ST

what is the relationship between Surface tension and temperature

• as temp rises = ST drops

what does surface tension tell us

• molecules at the surface are only pulled down and sideways

what is capillarity

the competition between 2 forces

what do cohesive forces do in liquids

pull the liquid toward itself

what do adhesive forces do in liquids

pull the liquid toward the tube wall

what shape a concave meniscus

U

what shaoe is a convex meniscus

upside down U → a hump

what type of meniscus is associated with cohesive forces

convex

what type of meniscus is associated with adhesive forces

concave

what is viscosity

resistance to flow

what is the relationship between IMF + surface area and viscosity

• stronger IMf + more surface area = higher viscosity

what is the relationship between temperature and viscosity

• higher temperature = lower viscosity (molecules have more kinetic energy)

what is vapor pressure

the pressure a vapor puts on a liquid or solid when the two are in a closed container

Nitrate

NO₃⁻

Nitrite

NO₂⁻

Sulfate

SO₄²⁻

Sulfite

SO₃²⁻

Phosphate

PO₄³⁻

Phosphite

PO₃³⁻

Carbonate

CO₃²⁻

Chlorate

ClO₃⁻

Chlorite

ClO₂⁻

Perchlorate

ClO₄⁻

Hypochlorite

ClO⁻

-ate vs -ite rule

-ite has one fewer oxygen than -ate; same charge

Per- prefix (oxyanions)

One more oxygen than -ate (perchlorate ClO₄⁻)

Hypo- prefix (oxyanions)

One fewer oxygen than -ite (hypochlorite ClO⁻)

-ate ion mnemonic

Nick the Camel ate a Clam for Supper in Phoenix: consonants = # of O, vowels = charge (NO₃⁻, CO₃²⁻, ClO₃⁻, SO₄²⁻, PO₄³⁻)

Ammonium

NH₄⁺

Hydroxide

OH⁻

Acetate

C₂H₃O₂⁻ (also CH₃COO⁻)

Dichromate

Cr₂O₇²⁻

Peroxide

O₂²⁻

Cyanide

CN⁻

Hydrogen carbonate (bicarbonate)

HCO₃⁻

Hydrogen sulfate (bisulfate)

HSO₄⁻

Hydrogen phosphate

HPO₄²⁻

Dihydrogen phosphate

H₂PO₄⁻

Adding H to a polyatomic ion

Each H added raises the charge by 1

Silver ion (fixed charge)

Ag⁺

Zinc ion (fixed charge)

Zn²⁺

Aluminum ion (fixed charge)

Al³⁺

Mercury(I) ion

Hg₂²⁺ (written as a pair, e.g. Hg₂Cl₂; don't reduce)

Acid naming: -ide anion

hydro___ic acid