Chapter 9: Chemical Names and Formulae

Monatomic ions: ionic compounds contain a positive (metal) ion and a negative nonmetal ion in a proportion such that their charges add up to zero. Examples:

Section 1: Naming Ions

Cations:

Cations: metals tend to lose valence electrons and therefore become positively charged. Group IA: Group IIA: Group IIIA:

Cations are the same name as the metal. Example:

9.1 (cont):

AnionsNonmetals tend to gain electrons and

become negatively charged ions called anions. Examples:The charge can be determined by

subtracting 8 from the group A number.

The name is not the same as the element, it starts with the stem of the element name and ends in –ide. Example:

9.1 (cont)

Many transition metals (B groups) form more than one cation with different ionic charges determined by the number of electrons lost. Examples:

There are two methods to name these cations: p542 Stock System: the newer preferred method

places Roman numerals in parentheses after the name of the element to indicate the charge. Example:

The older, classical system used the root of the element and added different suffixes. Example:

9.1 (cont)

Polyatomic ions:Composed of more than one atomBehaves as a unit like a monatomic ion

Carries a chargeOften ends in –ite or -ateExamples: see p 546

9.1 (cont)

Writing formulae for binary ionic compounds: Binary Ionic Compounds are composed of 2

elements First write the symbol of the cation and

then the anion Add subscripts as needed to balance the

charges of each. LCM method Crisscross or ‘switcheroo’ method (see p

555) examples

9.2: Naming and Writing Formulae for Ionic Compounds

Naming Binary Ionic Compounds Confirm that it is an ionic compound

(metal or ions present?) Place the cation name first followed by

the anion name Examples: If the metallic element has more than one

charge, a Roman numeral must be used. Examples:

9.2 (cont)

What about ionic compounds with polyatomic ions?

Write as you would the formula of a binary compounds using parentheses to indicate more than one polyatomic ion when needed.

Examples: When naming, you need to identify that there is

a polyatomic ion present (use chart on p 546) and then name as you would the binary ionic compounds.

Examples:

9.2 (cont)

Binary Molecular Compounds composed of 2 elements that are nonmetals and are not ions.

Electrons are shared, so ionic charges are not used in writing them.

Can combine in more than one way.Examples:

9.3 Naming and Writing Formulae for Molecular Compounds

Naming Binary Molecular Compounds

Write the names of the elements in the order listed in the formula

Use prefixes to indicate the number of each kind of atom (p569). The prefix mono is omitted for the first element.

End the name of the second element with the suffix –ide.

Examples:

9.3 (cont)

Writing Formulae for Binary Molecular Compounds:Use the prefixes to tell you the subscript of each element in the formula

Write the correct symbols for the 2 elements with the respective subscripts

Examples:

9.3 (cont)

Naming Compounds: Flow diagram on p 593

Writing Formulae for compounds: p595

9.4: The names of common acids are listed on p 580.

Summary for Naming and Writing Formulae

The Law of Definite Proportions: in samples of any chemical compound, the masses of the elements are always in the same proportion. This follows Dalton’s Theory which stated that if the atoms are in fixed whole-number ratios, then the masses are also fixed.

Example:

9.5 The Laws Governing How Compounds Form

Law of Multiple Proportions:Some compounds contain the same elements but have different properties

Whenever the same 2 elements form more than one compound the different masses of one element that combine with the same mass of the other element are in the ration of small whole numbers.

Example: Calculating Mass Ratios: see p 589-590

9.5 (cont)

NO, NO2