Unit 4: Bonding and Nomenclature

Unit 4:

Bonding and Nomenclature

Covalent, Ionic, Acidic, and Organic Compounds, Formula Mass, and

Percent Composition

The Covalent Bond

• The bond in which atoms are held together by their mutual electrical attraction for shared

electrons. It is created between the sharing of electrons of two non metals.

Fluorine

The Covalent Bond

■ A single covalent bond is made up of two electrons.

■ The covalent bond is represented using a straight line.

F — F

F F

Diatomic Molecules

■ A molecule is a neutral group of atoms joined together by covalent bonds.

■ Molecules made up of two atoms.

■ There are 7 diatomic molecules.

■ H

, N

, O

, F

, Cl

, Br

, I

Molecular Formula

■ A molecular formula is a chemical formula that is used for molecular (covalent)

compounds.

■ It shows the types and number of atoms in a molecule.

■ Note that ionic compounds used the chemical formula called the formula unit.

■ A molecular formula does not give information

about the molecules structure.

Molecular Formula

■

To name formula:

■

Name first element, use prefix if first element is more than 1 (never use MONO on 1

element). Then

name 2

element using prefix every time. Suffix on 2

element is –ide.

■

To write formula:

■

Write symbol of element and use prefix to get the subscript of the element.

■

It shows the types and number of atoms in a molecule.

■

A molecular formula does not give information about

the molecules structure.

Molecular Formula Prefixes and Examples

Examples

Name Formula

Diphosphorous pentoxide

P₂O₅

Carbon tetrachloride CCl₄

Dihydrogen monoxide

H₂O

Nitrogen trihydride NH₃

Boron trifluoride Dinitrogen tetroxide Silicon dioxide Sulfur hexaiodide

BF₃ N₂O₄ SiO₂ SI₆

Prefix Value (Subscript)

Mono 1 (no written

subscript, just the symbol)

Di 2

Tri 3

Tetra 4

Penta 5

Hexa 6

Hepta 7

Octa 8

Nona 9

Deca 10

Structural Formula

■ Structural formulas show the arrangement of atoms in a molecule.

■ In a structural formula, the electron pair is represented by a line

■ Example: H-H

(single bond: one pair of electrons)

Ionic Compounds Molecular Compounds Crystal Lattice Molecule

Types of Elements

Metal with non-metal or polyatomic ions

Non-metal with non-metal

Physical State

Solid Solid, liquid or gas Melting Point High

> 300 °C

Low

<300 °C Solubility in

water

Generally high Generally low Electrical

conductivity of solution

Good conductor Poor to none

Ionic Bonds

All ionic compounds are made from ionic bonds. Positive

cations and the negative anions are attracted to one another.

OPPOSITES ATTRACT!

Therefore, ionic compounds are usually between

metals and nonmetals (opposite ends of the periodic

table).

POLAR MOLECULES

■ In a polar molecule, one end of the molecule is slightly negative and one end is slightly positive.

■ A molecule with a center of negative charge

and a center of positive charge has a dipole

moment.

Binary Ionic Compounds

■ Made up of one metal and one nonmetal

■ Ex: NaCl, MgO, Al

O

Naming Ionic Compounds

1) Name the first element

2) Name the second element using its root and then add –ide to the end.

3) Use parenthesis with Roman numerals to

designate the oxidation state of a transition

metal.

Practice:

Naming Ionic Compounds

A) NaF

B) Al

O

C) Fe

O

D) CrCl

Writing Ionic Compounds

1) Write the oxidation number for each element as a superscript next to the symbol.

2) Add the oxidation numbers – if zero, just smush the symbols together to get the formula for the compound.

3) If oxidation numbers added up isn’t zero, swap superscripts making them subscripts on the

other element and cancel out the + or –

4) If the subscripts are divisible by 2, simplify the

formula.

Practice:

Writing Ionic Compounds

A) Aluminum phosphide

B) Barium chloride

C) Titanium (IV) sulfide

D) Potassium phosphide

E) Copper (II) nitride

Writing and Naming

Compounds Containing Polyatomic Ions (tertiary)

For Writing: SAME RULES APPLY AS FOR BINARY IONIC COMPOUNDS – just put parenthesis around the polyatomic ion before adding a subscript outside of it if necessary.

For naming: Name the first element (if off the periodic table), name the ion off the ion chart. DO NOT

CHANGE ITS ENDING!! It is helpful to memorize

common ones: hydroxide, ammonium, nitrate, sulfate,

sulfite, carbonate, nitrite, phosphate, phosphite.

Practice: Writing and Naming Compounds Containing

Polyatomic Ions (tertiary) 1) Lithium

phosphate

2) Barium nitrite 3) Aluminum

carbonate 4) Calcium

oxalate

5)Mg(NO ₃ ) ₂ 6)K ₂ SO ₄

7)NH ₄ F

8)Sr(OH) ₂

19

Acids -a molecular substance that dissolves in water to produce a hydrogen ion

acts like an ionic compounds because they break down into cations and anions in water

produces a characteristic anion for which it is named

If the anion ends with… -ide such as chloride, fluoride

add the prefix

hydro-

–ic

acid

If the anion ends with… -ate such as phosphate, sulfate

change the ending to

–ic

acid.

If the anion ends with… -ite such as sulfite, phosphite

change the ending to

–ous

acid

20

Acids Practice

1) HF

2) HNO

3) HClO

4) Oxalic acid

5) Hydroiodic acid

6) Sulfurous acid

7) Carbonic acid

8) Phosphoric acid

9) HC

H

O

■ Organic Chemistry- ^{study of}

carbon containing compounds.

■ Exceptions: oxides and carbonates

■ Unique bonding of Carbon

1)

four valence electrons

2)

relative small size, making covalent bonds very stable.

■ Properties of Organic Compounds

1)

insoluble in water

2)

low melting & boiling point

3)

Decompose easily with heat

4)

reacts with O

to produce CO

& H

O

(Combustion rxn)

Hydrocarbons- organic molecules that contain only carbon & hydrogen.

# Carbon Atoms Prefix 1 meth-

2 eth-

3 prop-

4 but-

5 pent-

6 hex-

7 hept-

8 oct-

9 non-

10 dec-

Saturated Hydrocarbon Alkanes

■ All carbon-carbon single bonds

■ General formula C

H

■ Straight chain alkane- all carbon-carbon bonds are connected in a single line.

■ Saturated hydrocarbon- carbon skeleton is filled to capacity with hydrogen atoms.

■ To name:

1) Use the prefixes to note # of carbons 2) Add the –ane ending.

Practice Problems

1) Write the name for C ₂ H ₆ &

C ₃ H _8.

2) Write the formula for butane & heptane.

3) Draw the lewis dot

(structural formulas) for C ₂ H _{6 ,} C ₃ H _8, butane &

heptane.

Branched Alkanes

■ Carbon chain is not in a straight line, it is branched.

To name:

1.

Find the longest continuous chain of carbon atoms (“parent chain”) and name it.

2.

Name the shorter chain with prefixes and –yl

ending, then specify location

Practice Problems

Write the chemical formula and name for each.

a)

b)

Cylcoalkane

■ Hydrocarbon with a carbon ring.

■ Single carbon-carbon bonds.

■ General formula C

H

■ To name:

1.

Use the prefixes to note # of carbon atoms

2.

Add the –ane ending

3.

Add cyclo- to the beginning of the name.

Practice Problems

1) Write the chemical formula for Cyclobutane, Cyclopentane, cyclohexane

2) Write the name for C

H

& C

H

3) Draw the lewis dot (structural formula) for Cyclobutane,

Cyclopentane, cyclohexane ^,

C

H

& C

H

Structural Isomers- same

Chemical formulas but

with different structural

formulas.

Unsaturated Hydrocarbons Alkenes

■ Contain a carbon-carbon double bond

■ General formula: C

H

■ To name:

1) Use the prefix to note the number of carbons 2) Add the –ene ending

3) Designate the location of the double bond.

■ A cyclic arrangement of 6 carbon atoms and 6

hydrogen atoms

■ exist as an individual molecule

■ usually found as part of larger molecules called aromatic

compounds

Benzene

■ A cyclic arrangement of 6 carbon atoms and 6

hydrogen atoms

Benzene

C₆H₆

Practice Problems

1) Write the name for C ₂ H ₄ & C ₃ H _6.

2) Write the chemical formula for 2-butene 3-hexene, & 4-heptene.

3) Draw the lewis dot (structural formulas) for

C

H

C

H

2-butene 3-hexene, & 4-heptene.

Unsaturated Hydrocarbons Alkynes

■ Contain a carbon-carbon triple bond

■ General formula: C _n H _2n-2

To name:

1)

Use the prefixes to note the number of carbon atoms

2)

Add the –yne ending

3)

Designate the location of the triple bond.

Practice Problems

1) Write the name for C ₂ H ₂ &

C ₃ H _4.

2) Write the formula for 3-butyne & 4-heptyne.

3) Draw the lewis dot

(structural formulas) for C ₂ H _{2 ,} C ₃ H _4, 3-butyne &

4-heptyne.

Substituted Hydrocarbons

■ Remove a hydrogen and add a –F, -Cl, -I, and –Br and give the carbon number and the

prefix fluoro, chloro, iodo, or bromo

■ To name:

1) Use the prefixes to note # of carbons

2) Give the carbon number and prefix first before the name. This type of substitution can come on

alkanes, alkenes, alkynes, or cyclics. Use the appropriate suffix depending on the type of bond.

Alcohols

■ Remove a hydrogen from an alkane, alkene, or alkyne and add a –OH in its place.

■ To name:

1) Use the prefixes to note # of carbons 2) Add the –ol ending.

3) Give the carbon number to locate the alcohol.

4) Prior to the ol, the type of bond is mentioned by –an for alkanes, -en for alkenes, or –yn for alkynes.

Formula Mass (aka Molar Mass) (aka Molecular Weight)

■ The mass of a compound

■ Calculated by:

■

Obtaining the atomic mass of each element from the periodic table

■

Multiplying the mass of each element by the subscript for that element given in the formula

■

Adding these masses together after multiplying

■

Giving the number the unit of g/mole (grams per mole). Remember NO

NAKED NUMBERS!!!

Molar Mass of Sodium Carbonate: Na

CO

Na 2 x 23.0 = 46.0

C 1 x 12.0 = 12.0

O 3 x 16.0 = 48.0

molar

mass = 106.0 g/mole

Molar Mass of Sodium Carbonate: Ca(NO

)

Ca 1 x 40.1 = 40.1

N 2 x 14.0 = 28.0

O 6 x 16.0 = 96.0

molar

mass = 164.1 g/mol

***Any time there is parenthesis in a formula the subscript outside the

parenthesis distributes when you multiply, just like in math class. Thus, the N, which originally has an understood 1, becomes a 2, and the O, which originally has a 3 as its subscript, becomes a 6. Then each is multiplied by their mass, but the 2 does not affect the calcium because it is on the opposite side of the parenthesis.

Calculating Percent Composition

1) Calculate the formula mass of the compound (also called the molar mass)

2) In doing so, you have the mass of each element in the compound.

3) Divide the mass of each element by the molar mass of the compound then multiply by

100%. This gives the percent composition for

each element in the compound.