Section 8.2 Naming Molecules

• Translate molecular formulas into binary molecular compound names.

oxyanion: a polyatomic ion in which an element (usually a nonmetal) is bonded to one or more oxygen atoms

oxyacid

• Name acidic solutions.

Specific rules are used when naming binary molecular compounds, binary acids, and oxyacids.

Why do atoms bond? (cont.)

• The chemical bond that results from sharing electrons is a covalent bond.

• A molecule is formed when two or more nonmetal atoms bond.

Gaining or losing electrons makes atoms more stable by forming ions with noble-gas electron configurations. (octet)

• Sharing valence electrons with other atoms also results in noble-gas electron configurations.

• Shared electrons are considered to be part of the outer energy level of all the atoms that share it.

• This type of bonding usually occurs between elements near each other on the periodic table.

• Most of this type of bonding is done with nonmentals.

Molecular Nomenclature (Naming)

• Prefix System (binary compounds)

1. Less electronegative atom comes first.

2. The first element is always named first using the entire element name.

3. Add prefixes to indicate the subscripts of each atom. Omit the mono- prefix on first element.

4. Change the ending of the second element to -ide.

PREFIXmono-di-tri-tetra-penta-hexa-hepta-octa-nona-deca-

NUMBER12345678910

Molecular Nomenclature

• Name the following: P2O5

– Name the two elements:• Phosphorus and Oxygen• For the second element, the name is

changed to oxide.• Add the prefixes to show the number

of atoms.

–Diphosphorus pentoxide

• Exception to the prefixes in table 8.3:– The first element never uses the mono prefix– If using a prefix would cause two consecutive

vowels, one of the them is often dropped to avoid a difficult pronunciation.• CO is monoxide NOT monooxide.

• CCl4

• N2O

• SF6

– carbon tetrachloride

– dinitrogen monoxide

– sulfur hexafluoride

Molecular Nomenclature

• arsenic trichloride

• dinitrogen pentoxide

• tetraphosphorus decoxide

– AsCl3

– N2O5

– P4O10

Molecular Nomenclature

N O F

Cl

Br

I

H

Molecular Nomenclature

• The Seven Diatomic Elements, exist naturally as 2 atom molecules

H2 N2 O2 F2 Cl2 Br2 I2

Naming Binary Molecular Compounds (cont.)

• Many compounds were discovered and given common names long before the present naming system was developed. (water H2O, ammonia NH3, hydrazine N2H4, and nitric oxide NO are examples).

• These compounds are generally known by their common names instead of their scientific ones. What would their scientific names be?

• Acids

– Compounds that form [H+] in Solution (water).

– Formulas begin with ‘H’.

• Examples:

– HCl – hydrochloric acid

– HNO3 – nitric acid

– H2SO3 – sulfurous acid

Naming Acids

Acid Nomenclature

• Anion Ending• -ide

• -ate

• -ite

• Acid Name– Hydro-(stem)-ic acid

– (stem)-ic acid

– (stem)-ous acid

• HBr

• H2CO3

• H2SO3

– Br ends in -ide

– CO3 ends in -ate

– SO3 ends in -ite

hydrobromic acid

carbonic acid

sulfurous acid

Acid Nomenclature

• hydrofluoric acid

• sulfuric acid

• nitrous acid

– Fluoride

– Sulfate

– Nitrite

HF

H2SO4

HNO2

H+ F-

H+ SO42-

H+ NO2-

Acid Nomenclature

Naming Acids (cont.)

• The second word is always acid.

Notice that hydrogen is not part of the name.

Naming Acids (cont.)

• An acid, whether a binary acid or an oxyacid, can have a common name in addition to its compound name.

A. A

B. B

C. C

D. D

Section 8-2

Section 8.2 Assessment

A B C D

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Give the name for the molecule HClO4.

A. perchloric acid

B. chloric acid

C. chlorous acid

D. hydrochloric acid