Chemistry Exam 2 Polyatomic Ions/Molecular Shapes

NH₄⁺

ammonium

PO₄^3-

Phosphate

C₂H₃O₂^-

Acetate

CN^-

Cyanide

NO₂^-

Nitrite

NO₃^-

Nitrate

OH^-

Hydroxide

MnO₄^-

Permanganate

ClO₄^-

Perchlorate

SO₃^2-

Sulfite

SO₄^2-

Sulfate

CO₃^2-

Carbonate

CrO₄^2-

Chromate

Rule of 7

H₂, start at 7 (N₂) and make a 7

SN = 2

Electron and molecular: linear geometry, max angle = 180 degrees

SN = 3

Electron and molecular: trigonal planar, max angle = 120 degrees

SN = 4

electron and molecular: Tetrahedral, max angle = 109.5

SN = 5

Electron and molecular: Trigonal bipyramidal, with three angles at 120 degrees and two at 90 degrees.

SN = 6

Octahedral, 90 degree bond angles

2 Bonds, 1 LP

electron geometry: trigonal planar

molecular geometry: bent

Two bonds, 2 LP

electron geometry: tetrahedral

moleculars geometry: bent

104.5 degree bond angle

2 Bonds, 3 LP

Electron geometry: trigonal bipyramidal

Molecular geometry: linear

180 degree bond angle

3 Bonds, 1 LP

Electron Geometry: tetrahedral

Molecular Geometry: trigonal pyramidal

Bond angle: 96.3

3 Bonds, 2 LP

Electron geometry: trigonal bipyramidal

Molecular geometry: T-shaped

4 Bonds, 1 LP

Electron geometry: trigonal bipyramidal

Molecular geometry: seesaw

Bond angle:

90° between axial–equatorial bonds

120° between equatorial–equatorial bonds

4 Bonds, 2 LP

Electron geometry: Octahedral

Molecular geometry: Square planar

Bond angle: slightly less than 90 degrees

5 Bonds, 1 LP

Electron geometry: Octahedral

Molecular geometry: Square-based pyramidal

Bond angle: slightly less than 90 degrees

Bonds forming…

Releases energy (exothermic)

Bonds breaking…

Consumes energy (endothermic)

What bonds are usually/always solids?

Ionic bonds

Lattice energy:

-found only in ionic compounds

Two things determine strength:

1. Charge on ions (absolute value, ignore signs and multiply)

2. Smaller radius = stronger L.E.

What determines polarity in a bond/molecule?

Difference in electronegativity across the bond. Look at the number of steps away from Fluorine (only horizontal and vertical).

What molecules are usually polar?

Anything with F or O, or one element closer to F than another.

What molecules are usually nonpolar?

Any element bonded to itself, elements next to each other besides O and F, same # of steps from F.

Naming Ionic Compounds:

No numerical prefixes.

If in main group, just put the name of the element. If a transition metal, determine charge and put the charge in roman numerals in parenthesis.

Naming Covalent Compounds:

Only second element gets prefix if one of each element, both elements get prefixes if from 2-10.

1- mono

2- di

3- tri

4- tetra

5-penta

6-hexa

7-hepta

8-octa

9-nona

10-deca

Sigma bonds:

-direct head to head bond overlap

-every bond order has one sigma bond

-dumbbells

Pi bonds:

-overlap of unhybridized p orbitals (double and triple bonds)

-slightly weaker than sigma bonds

-sp can allow for 2 pi bond formations, sp² can allow for 1 pi bond formation

Hybridization for SN = 2

sp

Hybridization for SN = 3

sp²

Hybridization for SN = 4

sp³

Hybridization for SN = 5

sp³d

Hybridization for SN = 6

sp³d²

Bond order:

(bonding-antibonding e)/2

Paramagnetic

Unpaired e- present in molecular orbitals

Diamagnetic

All e- paired in molecular orbitals

What leads to larger dipole moments?

Bigger/larger/extended molecules

Intermolecular forces

Forces between SEPARATE molecules. Broken when something is melted/boiled. Stronger charge = stronger IMFs.

Intramolecular forces

Forces within molecules. Stronger than intermolecular forces.

Strongest → weakest IMFs

1. Ion-Dipole force

between fully charged ion and dipole of opposite charge on polar molecule

2. Hydrogen bonding

very powerful dipole-dipole, can only occur if H is bonded to N, O, or F

3. Dipole-Dipole force

between opposite charged dipoles on separate polar molecules, more polar = stronger dipole-dipole

4. London Dispersion

present in all molecules, arise from “dipole moments”, bigger = stronger LDFs

Solubility: more OH groups means…

more soluble

Which is bigger: cations or anions?

Anions

Which bonds can be both ionic and covalent?

A polyatomic ion bonded to another ion.

Resonance structures have (longer/shorter, weaker/stronger) bonds

Resonance structures are always changing, so they have weaker and longer bonds. For instance, a double bond in a res structure is longer and weaker than a regular double bond.

Which bonds can form incomplete octets?

Boron (B), Aluminum (Al), and Tin (Sn) → “Buy All Snacks!”

Which element can take only 4 electrons?

Beryllium (Be) → “Best!”

From which group down can an expanded octet be had?

Group 3 and down.

Which elements in group 2 must follow the octet rule?

C, N, O, F

Where does H lie in terms of EN?

Between Boron and Carbon (B and C).

Do transition metals and nonmetals form polar and ionic bonds?

Yes

Do metalloids and nonmetals form polar and ionic bonds?

They are usually polar, but they form covalent bonds → polar covalent. Ex: SiO₂