chemical nomenclature - north seattle...

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Chemical

Nomenclature

Chapter 6

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007

Brooks/Cole, a part of the Thomson Corporation.

Section 6.1

Introduction to

Nomenclature



Nomenclature:A system of names used in a science.

The key to learning such a system

is to minimize memorization anddevelop an understanding of a

systematic procedure for naming

chemical compounds.



Section 6.2

Formulas of Elements



Given a name or formula of an element in Figure

5.9, write the other.

Goal 1



In Chapter 5 you learned the symbols of 35 elements. In

this chapter you will learn thechemical formulas of those elements.



2

Molecule:The tiniest independent particle of a pure substance.

For most elements, the smallest independent

particle is a single atom.Their formula is the elemental symbol.

Examples

Element Formula

Helium

Lithium

He

Li



Seven elements form diatomic moleculesunder normal conditions

Di- means two

The smallest particle of these elements

is two atoms that are chemically attached

to each other

The chemical formula of a diatomic molecule

is the elemental symbol followed by

a subscript of 2



7 elements occur in natureas diatomic (two-atom) molecules:

the formula of hydrogen is H2

the formula of nitrogen is N2

the formula of oxygen is O2

the formula of fluorine is F2

the formula of chlorine is Cl2

the formula of bromine is Br2

the formula of iodine is I2





Some other elements commonly form polyatomic

(many-atom) molecules. However, their natural molecular form varies, so we will write their formulas as

if they were monatomic (one-atom) species. This will not

affect calculations involving these elements.

Element Formula

carbonphosphorus

sulfur

CP

S



He



3

Cl2

P orP4



S orS8



C orC60



Section 6.3

Compounds Made from

Two Nonmetals



Given the name or formula of a binary molecular

compound, write the other.

Goal 2



Given the name or the formula of water, write the

other; given the name or the formula of ammonia,

write the other.

Goal 3



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The stair-step line in the periodic table separates elements on the left that are metals from elements on

the right that are nonmetals. Several elements

bordering on this line are metalloids or semimetals.

Compounds formed by two nonmetals or

a metalloid and a nonmetalare called binary molecular compounds.



Naming binary molecular compounds:

1. The first word is the name of the firstelement in the compound, modified with a

prefix to indicate the number of atoms

of that element in the molecule.

2. The second word is the name of the second

element in the compound, changed to end in-ide, modified with a prefix to indicate the

number of atoms of that element

in the molecule.



1

2

3

4

5

6

10

9

8

7

mono-

di-

tri-

tetra-

penta-

hexa-

hepta-

octa-

nona-

deca-Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007


Examples:

Write the name of I2O

5.

2 = di-

I = iodine

first word is diiodine

5 = penta-

O = oxygen

change 2nd word to end in -ide = oxide

second word is pentoxide

Answer: diiodine pentoxidePresentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Third Edition Copyright © 2007


Write the formula of nitrogen trifluoride.

No prefix on first word = mono- is implied: 1

The symbol of nitrogen is N

2nd word prefix tri- = 3

-fluoride is an “-ide modified” fluorine = F

Answer: NF3



Two important exceptions to the

binary molecular compound

nomenclature rules:

H2O is water

NH3

is ammonia



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Section 6.4

Names and Formulas

of Ions Formed by

One Element



Given the name or formula of an ion in Figure

6.3, write the other.

Goal 4



Figure 6.3



Ion:Charged particle formed when a neutral atom

or molecule loses or gains electrons

Cation:Positively-charged ion.

Formed when a neutral atom or molecule

loses one or more electrons.

Anion:Negatively-charged ion.

Formed when a neutral atom or moleculegains one or more electrons.



Monatomic ion:Ion formed from a single (mono-) atom

Formula of a monatomic ion:Elemental symbol followed by superscript

size of charge and sign of charge

(if the size of the charge is 1,the 1 is omitted)



Name of a monatomic cation:Name of element,

followed by the word ion

Name of a monatomic anion:Name of element changed to end in -ide,

followed by the word ion



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The charge on a main-group (U.S. A group) ion

corresponds to its group number:

Group 1A 2A 3A 5A 6A 7A

Charge 1+ 2+ 3+ 3– 2– 1–



Examples:What is the the formula of sodium ion?

Na+

Sodium is in Group 1A, so its ion has a 1+ charge

We write the symbol of the element,

followed by the charge in superscript,

omitting the 1



What is are the name and formula of the

ion formed from a sulfur atom?

A monatomic anion is named by changing the name of the

element to end in -ide, followed by the word ion:

sulfide ion

Sulfur is in Group 6A, so it forms 2– ions;

write the symbol of the element,

followed by the charge in superscript:

S2–



Many transition elements (U.S. B groups)

form multiple ions with different charges

All transition-element ions have a positive charge

To distinguish among the ions, the magnitude

of the charge is included with its name:

Cr2+ is chromium(II) ion

Cr3+ is chromium(III) ion



Three of the transition element ions

almost always occur with only one charge,

so chemists do not write the

magnitude of the charge in their names:

Ni2+ is nickel ion

Zn2+ is zinc ionAg+ is silver ion

You must memorize their charges



The mercury(I) ion is a special case:

it is a diatomic (two-atom) ion: Hg2

2+

It is named as if single atoms existed separately:

mercury(I) ion



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Example:

What is the formula of copper(II) ion?

What is the name of Zn2+?

The symbol for copper is Cu

(II) indicates the 2+ ion

Cu2+

The name of Zn is zinc

Zinc has just one common charge,

so its charge is not included in its name

zinc ion



Section 6.8

Formulas of

Ionic Compounds



Ionic compound:A combination of cations and anions that form a crystalline solid

Must be electrically neutral

Presentation Slides to Accompany Cracolice/Peters Introductory Chemistry: An Active Learning Approach, Second Edition Copyright © 2004

Brooks/Cole, a division of Thomson Learning, Inc.



How to Write the Formula of an Ionic Compound

Write the formula of the cation, followed by the formula of the anion, omitting the charges

Insert subscripts to show the number of each

ion needed in the formula unit to make thesum of the charges equal to zero with

the fewest number of ions possible

If only one ion is needed, omit the subscript

If a polyatomic ion is needed more than once, enclose

the formula of the ion in parentheses and place the

subscript after the closing parenthesis



Examples:

What is the formula of magnesium chloride?

MgCl2

Chlorine is in Group 7A/17, so chloride ion is Cl–

Two 1– ions are needed to balance the 2+ ion

Magnesium ion is in Group 2A/2, so its formula is Mg2+





Refer to this table for your Polyatomic ions. Some General Chemistry

Courses will require you to memorize most of these. Be prepared to do

that!!!

8

What is the formula of aluminum oxide?

Al2O3

The least common multiple of 2 and 3 is 6,

so 2 x 3+ balances 3 x 2–

Oxygen in in Group 6A/16, so

oxide ion is O2–

Aluminum is in Group 3A/13, so

aluminum ion is Al3+



What is the formula of barium nitrate?

Ba(NO3)2

Two 1– ions are needed to balance the charge

of the 2+ ion, and to retain the identity of

the nitrate ion, enclose it in parentheses

The formula of nitric acid is HNO3,

so nitrate ion is what results when the H+ is removed,

so it is a 1– ion, NO3

–

Barium is in Group 2A/2, so

barium ion is Mg2+



Section 6.9

Names of

Ionic Compounds



Given the formula of an ionic compound made up

of identifiable ions, write the name of the

compound.

Goal 9



How to Write the Name of an Ionic Compound

Write the name of the cation

Write the name of the anion

To name an ionic compound containing a metal

that commonly is capable of having morethan one ionic charge, the compound name

includes the charge of that metal



Examples:

Write the name of the following compound:

Zn(NO3)2

Zinc ion has only one common charge, 2+, so the magnitude

of the charge is not included in its name:

zinc ion

NO3

– comes from the memorized acid HNO3, nitric acid

-ic changes to -ate:

nitrate ion

zinc nitrate



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CoCl2

Examples:

Write the name of the following compound:

Cobalt ion has more than one common charge

Chlorine, Cl, is in Group 7A/17, so it forms

a 1– ion that ends in -ide:

chloride ion

Two 1– ions means the positive charge must be 2+:

cobalt(II) ion

cobalt(II) chloride



Section 6.11

Summary of the

Nomenclature System









Section 6.12

Common Names

of Chemicals



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