naming compounds and writing formulas

Naming Compounds and

Writing Formulas

Metals and Nonmetals For nomenclature purposes, metals are

to the left of the stair step line and nonmetals are to the right.

Systematic Naming

A compound is made of two or more elements.

The name should tell us how many and what type of atoms.

Types of Compounds The types of compounds you will learn

how to name and draw are ionic compounds (binary and

ternary), molecular compounds and acids (binary and ternary).

Atoms and Ions Atoms are electrically neutral. They have the same number of protons

and electrons. Ions are atoms, or groups of atoms,

with a charge. Ions have a different numbers of

electrons.

Anions An anion is a _________ ion. An anion has _______ electrons. Nonmetals can gain electrons. The charge is written as a superscript on

the right.

F1- Has gained ___ electron(s)

O2- Has gained ___ electron(s)

negativegained

1

2

Cations A cation is a _________ ion. It is formed by _______ electrons. There are more protons than electrons. Metals form cations.

K1+ Has lost ___ electron(s)

Ca2+ Has lost ___ electron(s)

positivelosing

1

2

Oxidation Numbers

IONIC COMPOUNDS

Naming Cations For cations, if the charge is always the

same (Group A) just write the name of the metal.

Li1+

Li is the symbol for ________.

Lithium is a Group 1A metal, so the charge is always the same. Write the name of the metal.

Li1+ is called the ___________.

Naming Cations

lithium

lithium ion

Sr2+

Sr is the symbol for __________.

Strontium is a Group 2A metal, so the charge is always the same. Write the name of the metal.

Sr2+ is called the _____________.

Naming Cations

strontium

strontium ion

Naming Cations Transition metals (as well as tin and

lead) can have more than one type of charge.

Indicate the charge with Roman numerals in parenthesis.

Zinc (Zn2+) and silver (Ag1+), although transition metals, only have one possible charge. Roman numerals ARE NOT used for zinc and silver.

Fe2+

Fe is the symbol for ______.

Iron is a transition metal, so the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis.

Fe2+ is called the ___________. iron (II) ion

iron

Naming Cations

Pb2+

Pb is the symbol for ______.

Lead is a Group 4A metal, and the charge is not always the same. Write the name of the metal, indicating the charge with Roman numerals in parenthesis.

Pb2+ is called the ___________.

Naming Cations

lead

lead (II) ion

1) Name the following cations.

a) Ca2+

c) Sn4+

Calcium ion

b) Al3+ Aluminum ion

Tin (IV) ion

Problem

Name the following ions.

d) Na1+

f) Cu1+

Sodium ion

e) Fe3+ Iron (III) ion

Copper (I) ion

Problem

Naming Anions Naming monatomic anions is always the

same. Change the element ending to – ide Example: F1- F is the symbol for fluorine, F1- is called

ide.fluor ine.

Cl-

Cl is the symbol for _________.

Chlorine is a Group 7A nonmetal, so the charge is always the same (-1).

Cl- is called the ____________.

Naming Anions

chlorine

chloride ion

O2-

O is the symbol for _________.

Oxygen is a Group 6A nonmetal, so the charge is always the same (-2).

O2- is called the __________.

Naming Anions

oxygen

oxide ion

Problem2) Name the following anions.

a) S2- sulfide ion

b) Br - bromide ion

Problem2) Name the following anions.

d) Se2- selenide ion

c) N3- nitride ion

Ionic Compounds In the formula for an ionic compound,

the symbol of the cation is written before that of the anion.

Subscripts, or small numbers written to the lower right of the chemical symbols, show the numbers of ions of each type present in a formula unit.

Naming Binary Ionic Compounds

Binary ionic compounds are composed of a metal bonded with a nonmetal.

Name the metal ion using a Roman numeral in parenthesis if necessary.

Follow this name with the name of the nonmetal ion.

3) Name the following binary ionic compounds.

a) NaCl sodium chloride

b) Ca3P2calcium phosphide

Problem

Name the following binary ionic compounds.

c) CuO Copper (II) oxide

d) SnBr2 Tin (II) bromide

Problem


e) Fe2S3 Iron (III) sulfide

f) AlF3 Aluminum fluoride

Problem


g) KCl Potassium chloride

h) Na3N Sodium nitride

Problem


i) CrN Chromium (III) nitride

j) PbO2Lead (IV) oxide

Problem

Writing Formulas for Cations

Write the formula for the metal. If a Roman numeral is in parenthesis

use that number for the charge. Indicate the charge with a superscript.

If no Roman numeral is given, find the Group A metal on the periodic table and determine the charge from the column number.

Nickel (II) ion

____ is the symbol for nickel.

Nickel is a transition metal, which is the reason why the charge with Roman numerals in parenthesis was included.

The formula for the nickel (II) ion is _____.

Ni


Ni2+

Gallium ion

____ is the symbol for gallium.

Gallium is a Group 3A metal and its charge is always the same (+3).

The formula for the gallium ion is ______.


Ga

Ga3+

4) Write the formulas for the following cations.

b) Copper (II) ion

a) Magnesium ion

c) Potassium ion

Mg2+

Cu2+

K1+

Problem

Write the formulas for the following ions.

e) Chromium (VI) ion

d) Silver ion

f) Mercury (II) ion

Ag1+

Cr6+

Hg2+

Problem

Writing Formulas for Anions

Write the formula for the nonmetal. Find the Group A nonmetal on the

periodic table and determine the charge from the column number.

Phosphide

___ is the symbol for phosphorus.

Looking at the periodic table and finding phosphorus, the oxidation number (charge) can be determined.

The formula for phosphide is _____.

P


P3-

Bromide

___ is the symbol for bromine.

The formula for bromide is _____.


Br

Br1-

Looking at the periodic table and finding bromine, the oxidation number (charge) can be determined.

5) Write the formulas for the following anions.

b) telluride

a) arsenide As3-

Te2-

Problem

Write the formulas for the following anions.

c) iodide ion

d) carbide ion C4-

Problem

I1-

Writing Formulas for Ionic Compounds

Oxidation numbers can be used to determine the chemical formulas for ionic compounds.

If the oxidation number of each ion is multiplied by the number of that ion present in a formula unit, and then the results are added, the sum must be zero.

Writing Formulas for Binary Ionic Compounds

Write the symbol for the metal. Determine the oxidation number from either the column number or the Roman numeral and write it as a superscript to the right of the metal’s symbol.


To the right of the metal’s symbol, write the symbol for the nonmetal. Determine the oxidation number from the column number and write it as a superscript to the right of the nonmetal’s symbol.


Example: potassium fluoride

K+

F -


If the two oxidation numbers add together to get zero, the formula is a one-to-one ratio of the elements.


Example: potassium fluoride

K + F -KF


Example: aluminum sulfide

Al 3+ S 2-


If the two oxidation numbers DO NOT add together to get zero, you will need to “criss-cross” the superscripts. These numbers now become subscripts.



Al 3+ S 2-

3+2-


Omit all positive and negative signs and omit all 1’s.



Al S2 3Al2S3

Problem

a) Lithium selenide

6) Write the formulas for the following binary ionic compounds.

b) Tin (II) oxide

Li2Se

SnO

Problem

c) Tin (IV) oxide

Write the formulas for the following binary ionic compounds.

d) Magnesium fluoride

SnO2

MgF2

Problem

e) Copper (II) sulfide


f) Iron (II) phosphide

CuS

Fe3P2

Problem

g) Gallium nitride


h) Iron (III) sulfide

GaN

Fe2S3

Naming Ternary Ionic Compounds

Ternary ionic compounds are composed of at least 3 elements.

Name the metal ion, using a Roman numeral in parenthesis if necessary.

Follow this name with the name of the polyatomic ion.

Polyatomic ions Polyatomic ions are groups of atoms

that stay together and have a charge. Examples are on page 7 of the

Reference Tables for Chemistry and include:Nitrate NO3

-

Nitrite NO2-

Hydroxide OH-

Ternary Ionic Compounds There is one polyatomic ion with a

positive oxidation number (NH4+) that

may come first in a compound. Name the ion, ammonium.

Follow this name with the name of the anion or second polyatomic ion.

Examples7) Name the following ternary ionic

compounds.a) LiCN

b) Fe(OH)3

Lithium cyanide

Iron (III) hydroxide

Examples Name the following ternary ionic

compounds.c) (NH4)2CO3 Ammonium carbonate

d) NiPO4 Nickel (III) phosphate

Problems Name the following ternary ionic

compounds.e) NaNO3 Sodium nitrate

f) CaSO4 Calcium sulfate

Problems Name the following ternary ionic

compounds.

g) (NH4)2O Ammonium oxide

h) CuSO3 Copper (II) sulfite

Writing Formulas for Ternary Ionic Compounds

Write the symbol for the metal or ammonium ion. Write the oxidation number as a superscript to the right of the metal’s/ammonium ion’s symbol.


To the right of the metal’s symbol, write the symbol for the nonmetal or polyatomic ion. Write the oxidation number as a superscript to the right of the nonmetal’s/polyatomic ion’s symbol.


Example: potassium nitrate

K + NO3-


If the two oxidation numbers add together to get zero, the formula is a one-to-one ratio of the elements.


Example: potassium nitrate

K + NO3-KNO3


Example: aluminum hydrogen sulfate

Al 3+ HSO4-


If the two oxidation numbers DO NOT add together to get zero, you will need to “criss-cross” the superscripts. These numbers now become subscripts.

Parentheses are to be placed around polyatomic ions before criss-crossing.



Al 3+ HSO4 -3+ -

( )


Omit all positive and negative signs and omit all 1’s.



Al(HSO4) 3Al(HSO4)3

Problems8) Write the formulas for the following

ternary ionic compounds.a) Ammonium chloride

b) Ammonium sulfide

NH4Cl

(NH4)2S

Problems Write the formulas for the following

ternary ionic compounds.c) Barium nitrate

d) Zinc iodate

Ba(NO3)2

Zn(IO3)2


ternary ionic compounds.e) Sodium hypochlorite

f) Chromium (III) acetate

NaClO

Cr(CH3COO)3 or Cr(C2H3O2)3


ternary ionic compounds.g) Iron (II) dichromate

h) Mercury (I) bromate

FeCr2O7

HgBrO3

STOP HERE

COVALENT (Molecular)

COMPOUNDS

Molecular Compounds

Molecular compounds are made of molecules.

They are made by joining nonmetal atoms together into molecules.

Naming is Easier

A molecular compound’s name tells you the number of atoms through the use of prefixes.

Prefixes 1 mono- 2 di- 3 tri- 4 tetra- 5 penta-

6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

Prefixes

The name will consist of two words.

Prefix name prefix name -ide

One exception is we don’t write mono- if there is only one of the first element.

Prefixes

The following double vowels cannot be used when writing names: (oa) (oo)

Example NO2

There is one nitrogen

mononitrogen

But, you cannot use mono- on the first element, so drop the prefix.

mononitrogen nitrogen

Example NO2

There are two oxygens

dioxygen

Example NO2

dioxygen

You need the suffix -ide

dioxygenide

Example NO2

nitrogen dioxide

Example N2O

There are two nitrogens

dinitrogen

There is one oxygen

monooxygen

Example N2O

monooxygen

You cannot run (oo) together, so

monoxygen

Example N2O

monoxygen

You need the suffix -ide

monoxygenide

Example N2O

dinitrogen monoxide

Problem9) Name the following molecular

compounds.

a) Cl2O7

b) CBr4

dichlorine heptoxide

carbon tetrabromide

Problem Name the following molecular

compounds.

c) CO2

d) BCl3

carbon dioxide

boron trichloride

Naming Molecular Compounds

You will not need to criss-cross oxidation numbers.

Molecular compounds name tells you the number of atoms through the use of prefixes.

Example diphosphorus pentoxide

The name implies there are 2 phosphorous atoms and 5 oxygens.

P2O5

Example sulfur hexaflouride

The name implies there is 1 sulfur atom and 6 fluorines.

SF6

Problem

10) Write the formulas for the following molecules.a) tetraiodine nonoxide

b) nitrogen trioxide

I4O9

NO3

Problem Write the formulas for the following

molecules.c) carbon tetrahydride

d) phosphorus trifluoride

CH4

PF3

Types of Compounds

Smallest piece

Melting Point

State

Types of elements

Formula Unit Molecule

Metal and nonmetal Nonmetals

Solid Solid, liquid or gas

High >300ºC Low <300ºC

Ionic Molecular

Acids

Writing Names and Formulas

Acids Acids are compounds that give off

hydrogen ions (H+) when dissolved in water.

Acids will always contain one or more hydrogen ions next to an anion.

The anion determines the name of the acid.

Naming Binary Acids Binary acids contain hydrogen and an

anion whose name ends in –ide. When naming the acid, put the prefix

hydro- and change -ide to -ic acid.

Example HCl

The acid contains the hydrogen ion and chloride ion.

Begin with the prefix hydro-, name the nonmetallic ion and change -ide to -ic acid.

hydrochlorideic acid

Example H2S

The acid contains the hydrogen ion and sulfide ion.

Begin with the prefix hydro- and name the nonmetallic ion.

hydrosulfide

Example H2S

The next step is change -ide to -ic acid, but for sulfur the “ur” is added before -ic.

hydrosulfideic acidur

Problem

a) HF

b) H3P(hydrophosphoric acid)

(hydrofluoric acid)

11. Name the following binary acids.

Writing the Formulas for Binary Acids

The prefix hydro- lets you know the acid is binary.

Determine whether you need to criss-cross the oxidation numbers of hydrogen and the nonmetal.

Example Hydrobromic acid

The acid contains the hydrogen ion and the bromide ion.

Example Hydrobromic acid

H1+Br1-

The two oxidation numbers add together to get zero.

HBr

Example Hydrotelluric acid

The prefix hydro- lets you know the acid is binary.

The acid contains the hydrogen ion and the telluride ion.

Example Hydrotelluric acid

H1+Te2-

The two oxidation numbers do NOT add together to get zero, so you must criss-cross.

H2Te

Problem12) Write the formulas for the following

binary acids.a) Hydrocyanic acid HCN

b) Hydroselenic acid H2Se

Naming Ternary Acids The acid is a ternary acid if the anion

has oxygen in it. The anion ends in -ate or -ite. Change the suffix -ate to -ic acid Change the suffix -ite to -ous acid The hydro- prefix is NOT used!

Example HNO3

The acid contains the hydrogen ion and nitrate ion.

Name the polyatomic ion and change -ate to -ic acid.

nitrateic acid

Example HNO2

The acid contains the hydrogen ion and nitrite ion.

Name the polyatomic ion and change -ite to -ous acid.

nitriteous acid

Example H3PO4

The acid contains the hydrogen ion and phosphate ion.

Name the polyatomic ion and change -ate to -ic acid.

phosphateoric acid

Problem

a) H2CO3

b) H2SO4

(carbonic acid)

(sulfuric acid)

13) Name the following ternary acids.

Problem

c) H2CrO4

d) HClO2

(chromic acid)

(chlorous acid)

Name the following ternary acids.

Writing the Formulas for Ternary Acids

The lack of the prefix hydro- from the name implies the acid is ternary, made of the hydrogen ion and a polyatomic ion.

Determine whether you need to criss-cross the oxidation numbers of hydrogen and the polyatomic ion.

Example Acetic acid

H1+C2H3O21-

The polyatomic ion must end in –ate since the acid ends in -ic.

The acid is made of H+ and the acetate ion.

Example

The two charges when added equal zero.

H1+C2H3O21-

HC2H3O2

Example Sulfurous acid

Again the lack of the prefix hydro- implies the acid is ternary, made of the hydrogen ion and a polyatomic ion.

Example sulfurous acid

H1+SO32-

The polyatomic ion must end in –ite since the acid ends in -ous.

The acid is made of H+ and the sulfite ion.

Example

The two charges when added do not equal zero, so you must crisscross the oxidation numbers.

H1+SO32-

Example

Ignore the negative sign and ones are understood.

H1+SO32-

H2SO3

Problem14) Write the formulas for the following

ternary acids.a) perchloric acid HClO4

b) iodic acid HIO3

Problem Write the formulas for the following

ternary acids.c) dichromic acid H2Cr2O7

d) hypochlorous acid HClO

naming compounds and writing formulas

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