Chemical Names and Formulas

Chapter 9

◦ A rose is rosa in Spanish, warda in Arabic, and julab in Hindi. To truly understand another culture, you must first learn the language used in that culture. Similarly, to understand chemistry, you must learn its language. For this you need to know how to name ions.

9.1 Naming Ions9.1

◦ Monatomic ions consist of a single atom with a positive or negative charge resulting from the loss or gain of one or more valence electrons, respectively.

Monatomic Ions9.1

Monatomic Ions9.1

◦ Many transition metals are multivalent: they can lose electrons from inner sublevels as well as the valence shell.

◦ Therefore the charges of the cations must be determined from the number of electrons lost. They form colorful compounds.

Monatomic Ions9.1

These colorful solutions contain the transition metal ions Co3+, Cr3+, Fe3+, Ni2+, and Mn2+.

Monatomic Ions9.1

Many transition metal compounds are colored and can be used as pigments.

Monatomic Ions9.1

◦ Two methods are used to name the ions of transition metals. The Stock system The Traditional system

Monatomic Ions9.1

In the Stock system, a Roman numeral in parentheses is placed after the name of the element to indicate the numerical value of the charge. This is only necessary for multivalent metals.

In an older method, the classical name of the element is used to form the root name.

Monatomic Ions9.1

Monatomic Ions9.1

Conceptual Problem 9.1 pg 256

1.1

Practice Problems pg 256

2. How many electrons were lost or gained to form these ions?a. Fe3+ b. O2- c. Cu+

Some ions, called polyatomic ions, are composed of more than one atom covalently bonded together.◦ The names of most negative polyatomic ions end

in -ite or -ate.

◦ The names of most positive polyatomic ions end in –ium.

Reference table E has formulas and names.

Polyatomic Ions9.1

These models show the structures of four common polyatomic ions.

Polyatomic Ions9.1

Sodium hydrogen carbonate can relieve an upset stomach.

Polyatomic Ions9.1

HCO3–, HPO4

2–, and H2PO4– ions in your blood are

critical for your health.

Polyatomic Ions9.1

Fertilizers contain HPO42– and H2PO4

– ions.

Polyatomic Ions9.1

A recipe is a formula for the sauce—a complete list of ingredients and their proportions. Chemistry also uses formulas. Once you know the rules, you can write the formula for any chemical compound.

9.2 Naming and Writing Formulas for Ionic Compounds

9.2

These masks are made of an ionic compound with the common name gypsum. This name does not tell you anything about the chemical composition of the compound, though.

Binary Ionic Compounds9.2

A binary compound is composed of two elements and can be either ionic or molecular.

To name any binary ionic compound, place the cation name first, followed by the anion name.

*remember to use parenthesis and a Roman numeral for multivalent metals.

Binary Ionic Compounds9.2

Tin(II) fluoride, or SnF2, is added to toothpastes to prevent cavities.

Binary Ionic Compounds9.2

Tin(IV) sulfide, or SnS2, is used in glazes for porcelain fixtures and dishes.

Binary Ionic Compounds9.2

Hematite, a common ore of iron, contains iron (III) oxide. The formula is Fe2O3.

Binary Ionic Compounds9.2

◦ Writing Formulas for Binary Ionic Compounds Write the symbol of the cation and then the anion. Cross the charges down to become subscripts and

reduce. If correctly written the sum of the charges in the formula

will be zero (compounds are neutral).

Binary Ionic Compounds9.2

Conceptual Problem 9.2 pg 2639.2

Practice problems pg. 263

for Conceptual Problem 9.2

10. Write formulas for compounds formed from these pairs of ions.

a. Ba2+ , S2- b. Li+ , O2-

c. Ca2+ , N3- d. Cu2+ , I-

◦ Write the formula for the cation followed by the formula for the anion and balance the charges (crisscross and reduce). Use parentheses around polyatomic ions when the

subscript is greater than one.

Compounds With Polyatomic Ions

9.2

Oysters produce calcium carbonate to form their shells and sometimes pearls.

Compounds With Polyatomic Ions

9.2

Lead(II)sulfate is an important component of an automobile battery.

Compounds With Polyatomic Ions

9.2

Conceptual Problem 9.3 pg. 265

9.3

Practice Problems pg. 265

for Conceptual Problem 9.3

13. Write formulas for these compounds.a. Lithium hydrogen sulfateb. Chromium (III) nitrite

◦ To name a compound containing a polyatomic ion, name the cation first and then the anion, just as you did in naming binary ionic compounds.

Use reference table E to help with names.

Compounds With Polyatomic Ions

9.2

Sodium hypochlorite (NaClO) is used as a disinfectant for swimming pools. The metallic cation in this compound is sodium (Na+) so the polyatomic ion must be ClO–.

Compounds With Polyatomic Ions

9.2

Write formulas:◦ Beryllium chloride◦ Cesium sulfide◦ Sodium iodide◦ Strontium oxide◦ Chromium (III) nitrite◦ Sodium perchlorate◦ Magnesium hydrogen carbonate◦ Calcium acetate

Try these

9.3 Naming and Writing Formulas for Molecular Compounds

One milligram of gold is worth only about one cent, but one kilogram of gold is worth approximately $12,500. The correct prefix ( milli- or kilo-) makes quite a difference! Prefixes are important in chemistry, too. The prefixes in the name of a binary molecular compound tell you its composition.

9.3

Carbon and oxygen combine to form carbon monoxide (CO) and carbon dioxide (CO2), but these two invisible gases are very different.

Naming Binary Molecular Compounds

9.3

Sitting in a room with small amounts of CO2 in the air would not present any problems. If the same amount of CO were in the room, you could die of asphyxiation. A naming system that distinguishes between these two compounds is needed.

Naming Binary Molecular Compounds

9.3

A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound.

Naming Binary Molecular Compounds

9.3

◦ Guidelines: Name the elements in the order listed in the formula. Use prefixes to indicate the number of each kind of

atom. Omit the prefix mono- when the formula contains

only one atom of the first element in the name. The suffix of the name of the second element is -ide.

Naming Binary Molecular Compounds

9.3

Name these compounds:◦ CCl4◦ N2O4

◦ PCl3◦ SO2

◦ P2O5

◦ H2O

◦ CH4

◦ NH3

Naming Binary Molecular Compounds

◦ Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts.

Writing Formulas for BinaryMolecular Compounds

9.3

Silicon carbide is a hard material like diamond. The name silicon carbide has no prefixes, so the subscripts of silicon and carbon must be one. Thus, the formula for silicon carbide is SiC.

Writing Formulas for BinaryMolecular Compounds

9.3

Write formulas for these compounds:◦ Sulfur trioxide◦ Hydrogen iodide◦ Diboron tetrabromide◦ Carbon tetrafluoride◦ Phosphorous triiodide◦ Antimony tribromide◦ Dihydrogen sulfide◦ Hexaboron silicide

Writing Formulas for BinaryMolecular Compounds