Unit 3 Notes Guide – Part 2 Name # Molecules Date: ____________________ Block: Chemistry

I. Chemical Formulasa. Atoms vs. Molecules

i. Atoms are the ________________ unit of matter consisting of _______________

and a nucleus made up of _____________ and ________________.

ii. Molecules are groups of ___________ bonded together.

b. Elements vs. Compounds

i. An element consists of _______ type of atom defined by the number of

____________ in the nucleus.

An element can be found as an ______ or as a ______________

_____________

ii. A compound consists of ________ than one type of atom

A compound can ________ be found as a molecule

II. Molecular vs. Empirical Formulasa. Molecular Formula – the ________ chemical formula of a substance

b. Empirical Formula – the ________________ ratio of elements in the molecular formula

c. Molecular formula Empirical formula

i. Divide the subscripts by the ________________ ____________ ____________ (GCF)

ii.

Examples:

d. Empirical formula Molecular formula

i. You must be given the empirical formula and the molar mass of the molecular formula (also

called the molecular mass)

Formula Molar Mass GCF

MF Step 3 42.03 g/molStep 2

EF CH2 Step 1

1. Find the __________ ________ of the empirical formula

2. ____________ the molar mass of the MF by the molar mass of the EF to find the GCF1

CO2

Substance Molecular Formula Simplify the Ratio Empirical Formula

Sugar C6H12O6C 6

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H 126

O66

C H2 O

Water H2O H 21

O 11

H 2O

3. _______________ the subscripts of the empirical formula by the GCF

III. Diatomic Moleculesa. Diatomic molecules are a special type of molecule consisting of ______ atoms of the _________

element bonded together (though they are still

considered an element!)

b. There are ______ diatomic molecules:

Br2 I2 N2 Cl2 H2 O2 F2

IV. Polyatomic Ionsa. A polyatomic ion is a _________________ chemical species

(ion) made up of ______ or ________ atoms bonded together.

b. Memorize these!

i. N ick the Camel ate Supper in Phoenix

Vowels = charge

Consonants = # oxygens

V. Metals vs. Nonmetalsa. There are three types of elements on the periodic table grouped by their chemical properties:

i. Metals

Metals are located on the _________ of the periodic table.

Properties of Metals:

a. Good ______________ of heat and electricity

b. High _________________ and

________________ points

c. High density

d. Hard

ii. Nonmetals

Nonmetals are located on the _________ of the

periodic table

Properties of Nonmetals:

a. Good _________________ (poor

conductors)

b. Brittle or gaseous

Practice #1: Identify the following as a metal or a nonmetal.

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Ammonium NH4+

Hydroxide OH-

Acetate C2H3O2-

Nitrite NO2-

Nitrate NO3-

Carbonate CO32-

Sulfite SO32-

Sulfate SO42-

Phosphate PO43-

Na C

F Zn

iii. Metalloids

Metalloids have properties of ______ metals and nonmetals.

They are located along the “________________” between

metals and nonmetals.

Some metalloids are ___________________________.

VI. Ionic Bondinga. Ionic Bonds form when electrons are _____________________ between two atoms

b. Electronegativity is a chemical property that describes an element’s ability to ________ electrons.

i. Nonmetals have ________ electronegativity (they tend to gain electrons)

ii. Metals have ______ electronegativity (they tend to lose electrons)

c. Ionic bonds form from the interaction of ions

i. How do charges interact?

______ charges repel but opposite charges ____________.

d. Ionic bonds can only form between a ___________ and an _________

i. An element forms a cation when it _________ electrons, so we need an element with

_________ electronegativity

___________ easily lost electrons, so they are the most likely source of __________

ii. To gain an electron, an element must have a _________ electronegativity. Therefore,

_________________ are the most likely source of ____________.

Ionic Bond = cation + anion

Ionic Bond = ______________ + ____________________e. Drawing Ionic Bonds

i. We can use Lewis dot diagrams or Bohr models to

represent ionic bonds

ii. The arrow indicates where the ___________ is

transferred _____

iii. It can also represent _____________ atoms donating

______________ electrons.

Practice #2: Draw the ionic bonds formed for each as a Lewis Dot diagram with arrows.KBr K Br CaCl2

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Cl Ca Cl

VII. Ionic Nomenclaturea. A binary compound is a compound containing only ______ elements.

b. Ionic compounds are named so that the ____________ ion (_________) comes first and the

_______________ ion (______________) comes last ending in -______.

Metal + Nonmetal-ideExamples

NaCl Sodium chloride

CaBr2 Calcium bromide

K3P Potassium phosphide

LiO Lithium Oxide

Ag2S Silver sulfide

c. Naming with Transition Metals

i. Main group elements always form the same ion with the same __________.

ii. Transition metals can form ions with _______________ different charges.

iii. You determine the charge on a transition metal using algebra. Remember, the charges have to

add up to 0 for the compound to be neutral!

(# metal atoms)(charge of metal) + (# anions)(charge of anion) = 0Examples

CuO1x + 1(-2) = 0

x – 2 = 0x = +2

Fe3P2

3x + 2(-3) = 03x – 6 = 0

x = +2

PbO2

1x + 2(-2) = 0x – 4 = 0x = +4

Cu2SO4

2x + 1(-2) = 02x – 2 = 0

x = +1

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Practice #3

KCl

CaO

K2S

NaF

BaBr2

Practice #4

NiBr

Cu2S

PbSO4

iv. When naming compounds with transition metals, we have to indicate the charge by using roman

numerals (I, II, III, IV, V, VI, VII, etc.)

Transition metal (Roman #) + Nonmetal-ideExamples

CuO Copper (II) oxide

PbO2 Lead (IV) oxide

Fe3P2 Iron (II) phosphide

v. There are _______ exceptions to the roman numeral rule:

Cadmium (______)

Zinc (______)

Silver (______)

a. Naming with Polyatomic Ions

vi. The name of the polyatomic is used

________________ any changes to the ending

vii. Remember, the _______________ ion always comes

first!

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Practice #5

Cu2S

NiBr

FeCl3

Examples

NaOH Sodium hydroxide

CaCO3 Calcium carbonate

NH4OH Ammonium hydroxide

Practice #6

CaSO4

K3PO4

NH4Cl

b. Summary: Steps to naming ionic compounds

1. Write the name of the positive ion (metal or polyatomic)

2. Include a roman numeral in parentheses for transition metals to indicate charge

3. Write the name of the negative ion (nonmetal or polyatomic)

Change nonmetal names to end in -ide

VIII. Writing Ionic Formulasa. Steps to writing ionic formulas:

1. Write the cation and anion with their ___________ as superscripts

2. _________ & __________ the absolute value of the charges to become the subscript on the

opposite ion

3. If necessary, _____________ the subscripts by dividing by the greatest common factor

*Polyatomic ions should be put in parentheses if there are multiple*

Examples

Sodium chloride Na+ Cl- Na1Cl1 NaCl

Calcium phosphide Ca2+ P3- Ca3P2 Ca3P2

Magnesium oxide Mg2+ O2- Mg2O2 MgO

Silver sulfide Ag+ S2- Ag2S Ag2S

Magnesium hydroxide Mg2+ OH- Mg1(OH)2 Mg(OH)2

Lead (I) oxide Pb+ O2- Pb2O1 Pb2O

Magnesium sulfate Mg2+ SO42- Mg2(SO4)2 MgSO4

Practice #7

Lithium bromide

Calcium sulfide

Ammonium chloride

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Na2OO2-Na+

Magnesium carbonate

Cobalt (III) sulfide

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