Chem midterm practice

What is Ammonia( NH3)

weak base

What is Acetic Acid (HC2H3O2)

a weak acid

ion F-

Fluoride

Ammonium

NH4+

Cyanide

CN -1

Peroxide

O2 2-

Chemical bonds form to _____________ the potential energy of charged particles in atoms

reduce

Molecular formula: exact, actual number of each __________ in the molecule

atom

Empirical formula: simplest ___________________ ratio of the atoms

whole number

Lewis Dot Structure of Neon

Molar mass =

(the number of atoms of each element) × (the molar mass of each element)

ion Cl-

Chloride

ion Br-

Bromide

ion I-

Iodide

O2-

Oxide

S2-

Sulfide

N3-

Nitride

P3-

Phosphide

Acetate

C2H3O2-

Carbonate

CO3 2-

Hydrogen Carbonate

HCO3-

Hydroxide

OH-

Nitrite

NO2-

Nitrate

NO3-

Chromate

CrO4 2-

Dichromate

Cr2O7 2-

Phosphate

PO4 3-

Hydrogen Phosphate

HPO4 2-

Dihydrogen Phosphate

H2PO4 -1

Hypochlorite

ClO-

Chlorite

ClO2 -1

Chlorate

ClO3 -1

Perchlorate

ClO4 -1

Permanganate

MnO4 -1

Sulfite

SO3 2-

Hydrogen sulfite ion

HSO3 -1

Sulfate

SO4 2-

Hydrogen Sulfate

HSO4 -1

Generally, we write the name of the element ___________ first

of the smallest group number

If the two elements lie in the same group, we write the element with ___________ first

the greatest row number

prefix for 1 atom present

mono

prefix for 2 atoms

di

prefix for 3 atoms

tri

prefix for 4 atoms

tetra

prefix for 5 atoms

penta

prefix for 6 atoms

hexa

Prefix for 7 atoms

hepta

prefix for 8 atoms

octa

prefix for 9 atoms

nona

prefix for 10 atoms

deca

If there is only one atom of the first element in the formula

omit mono

Chemical bonds hold ________ together in molecules

atoms

Covalent bonding Electrons are _____________ between nuclei

shared

Covalent bonds form between

nonmetals

The smallest unit of a covalent compound is called a ________________

molecule

Ionic Bonding Electrons are ___________________ from one atom to another

transferred

Ionic bonds form between

metals & nonmetals

Cations and anions are ______ to each other

attracted

The smallest unit of an ionic compound is called a

formula unit

Structural formula: shows

connectivity of atoms and may indicate geometry

A Lewis dot structure is a structural model where each dot is represents a

valence electron

A Lewis dot structure is a structural model where each line represents

bond

Lewis Dot Structure of Lithium

Lewis Dot Structure of beryllium

Lewis Dot Structure of Boron

Lewis Dot Structure of Carbon

Lewis Dot Structure of Nitrogen

Lewis Dot Structure of Oxygen

Lewis Dot Structure of Florine

covalent single, double, triple bonds lewis structure

Formula mass: the mass of all of the ______________ in a compound (in atomic mass units)

atoms

Molar mass: the mass of 1 ______________ of a molecule or formula unit (in grams)

mole

1. Formula of compound from percent composition

1. Assume 100 g sample of compound

2. Calculate moles of each element in the 100 g sample

3. Determine the empirical formula (the mole ratio)

4. Determine the molecular formula based on the compound's molar mass and the molar mass of

the empirical formula

2. Formula of compound from decomposition data

1. Convert masses of each element in the sample to moles of each element

2. Use the moles of each element to determine the mole ratio (empirical formula)

3. Determine the molecular formula based on the molar mass of the compound and the molar

mass of the empirical formula

Formula of compound from combustion analysis

1. Determine the moles of carbon in the CO2 product

2. Determine the moles of hydrogen in the H2O

product

3. Convert moles of C and H to grams of C and H in

the product

4. Determine the mass of oxygen using the mass of

C, mass of H, and the total mass of the sample

5. Determine the empirical formula (the mole ratio of

C to H to O

6. Determine the molecular formula using the molar mass of the compound (if provided) and the

molar mass of the empirical formula.

Electronegativity is the ability of an atom to attract _______________ electrons toward itself in a chemical bond

shared

Periodic table trends: Electronegativity(generally) ____________from left to right across a period

increases

Periodic table trends: Electronegativity(generally) ____________ down a group

decreases

the formation of covalent bonds ___________________ energy

releases

Bond energy:

the average energy required to break 1 mole of a bond in the gas phase (units: kJ/mol)

For a pair of atoms, more shared electrons will correspond to a _______________ bond

stronger

Triple bond = largest bond energy = _____________ bond

Single bond = lowest bond energy = _____________ bond

strongest

weakest

Bond Length

average distance between two specific nuclei across many compounds

Depends on elements in the bond and number of shared electrons

Lewis Structures for Molecules

1. Arrange atoms in a skeleton structure

2. Count valence electrons in the molecule

3. Distribute bonding electrons and then nonbonding electrons to complete octets and duets

4. Form double bonds and triple bonds as needed to complete octets

5. Check the electron count

Resonance structures

Two or more Lewis structures

where the same atoms are in the same arrangement but

some electrons are not in the same places.

Formal Charge

the calculated charge an atom in a particular molecule would have if all of its

bonding electrons were equally shared

formal charge calculation

formal charge = (valence electrons in atom alone) - (valence electrons "owned" by atom in lewis structure)

formal charge rules

1. The sum of the formal charges on all atoms in a molecule or polyatomic atom must be equal to

the overall charge of the molecule (0) or ion.

2. The arrangement of atoms in a molecule will minimize the number of non-zero formal charges

and minimizes the magnitude of formal charges.

3. Negative formal charges are generally on the most electronegative atom(s) in a molecule.

exceptions to oclet rule

1. Odd number of electrons

Ex. Nitrogen monoxide, NO

full oxygen, nitrogen 7 valence

exceptions to oclet rule

2. Incomplete octet (open shell)

Ex. Boron trihydride, BH3

hydrogen full duet, boron 6 valence

3. Expanded octet

• Only atoms in period 3 or below (valence electrons in n≥3)

• Octet of the central atom is expanded

• Ex. Sulfur hexafluoride, SF6

sextet

VESPR 2 electron groups (electron geometry)

linear geometry

VESPR 3 electron groups (electron geometry)

trigonal planar geometry

VESPR 4 electron groups (electron geometry)

tetrahedral geometry

VESPR 5 electron groups (electron geometry)

trigonal bipyramidal geometry

VESPR 6 electron groups (electron geometry)

octahedral geometry

VESPR lone pair effects

Lone pairs occupy more space than bonding pairs and compress bond angles

• The bond angle decreases as the number of lone pairs increases.

VESPR Tetrahedral electron arrangement with 1 lone pair

electron geometry tetrahedral, molecular trigonal pyramidal

VESPR Tetrahedral electron arrangement with 2 lone pairs

electron geometry tetrahedral, molecular BENT

VSEPR Theory: Predicting molecular geometries

1. Lewis structure

2. Count electron groups around the central atom and determine electron pair geometry (electron

arrangement)

4. Determine number of bonding groups and lone pairs around the central atom

5. Determine molecular geometry and bond angles around central atom