copyright © houghton mifflin company. all rights reserved. 2 | 1 an ionic compound is composed of...

Copyright © Houghton Mifflin Company. All rights reserved. 2 | 1

• An ionic compound is composed of cations and anions.

• Ions are arranged in a repeating three-dimensional pattern, forming a crystal.

• The formula of an ionic compound gives the smallest possible integer number of ions in the substance (without writing charges) so that the combination is electrically neutral.

• The formula gives the formula unit of the compounds. A formula unit is not a molecule!


• What is formula of the ionic compound of Mg2+ and N3-?

The common multiple of the charges is 6, so we need three Mg2+ and two N3-. The resulting formula is

Mg3N2


• What is the formula of the ionic compound of Ca2+ and PO4

3-?

The common multiple of the charges is 6, so we need three Ca2+ and two PO4

3-. The resulting formula is

Ca3(PO4)2


• Organic Compounds

• An important class of molecular substances; they contain carbon combined with other elements – notably hydrogen, oxygen, and nitrogen.

• Hydrocarbons contain only carbon and hydrogen.


• A functional group is a reactive portion of a molecule that undergoes predictable reactions.

ExamplesName of Group

Functional Group

Methyl alcoholAlcoholOH

Dimethyl etherEtherO

Acetic acidCarboxylic acid

C

O

OH


• Chemical nomenclature is the systematic naming of chemical compounds.

• Compounds that are not organic are called inorganic compounds.

Carbon monoxide, carbon dioxide, carbonates, and cyanides are also classified as inorganic compounds.


• Naming Inorganic Compounds

1.Name the cation.2.Name the anion.


• Monatomic ions

• Ions formed from a single atom.

• Common monatomic ions are listed on the next slide by group and by period.


Common Monatomic Ions of the Main-Group Elements

Bi3+Pb2+Tl3+, Tl+

Ba2+Cs+

I-Te2-Sn2+In3+Sr2+Rb+

Br-Se2-Ga3+Ca2+K+

Cl-S2-Al3+Mg2+Na+

F-O2-N3-Be2+Li+

H-

6

5

4

3

2

1

VIIAVIAVAIVAIIIAIIAIAPeriod


• Rules for Predicting the Charge on a Monatomic Ion

• 1. Most main-group metals have one monatomic ions with a charge equal to the group number.

Al, in Group IIIA(3), has one ion, Al3+.Sr, in Group IIA(2), has one ion, Sr2+.K, in Group IA(1), has one ion, K+.


• 2. Some main-group metals with high atomic number have more than one cation. One cation will have the charge of the group number minus 2; the second cation will have a charge equal to the group number

Pb in Group IVA(14) has two ions:Pb2+ and Pb4+

Tl in Group IIIA(13) has two ions:Tl+ and Tl3+


• 3. Most transition metals form more than one cation, of which one is +2.

Zn and Cd form only the +2 ion.Ag forms only the +1 ion.

• 4. Nonmetal main-group elements form one monatomic anion with a charge equal to the group number minus 8.

F in Group VIIA(17) forms the F- ion.S in Group VIA(16) forms the S2- ion.N in Group VA(15) forms the N3- ion.


• Naming Monatomic Ions

• Monatomic cations are named after the element if the element forms only one cation.


• If more than one cation forms:a.In the Stock system, the charge is written using a

Roman numeral and is enclosed in parentheses.Cu2+ is copper(II).Cu+ is copper(I).

b.In an older system, the suffic –ic (for the higher-charged cation) or –ous for the lower-charged cation) is added to the element’s stem.

Cu2+ is cupric.Cu+ is cuprous.


• Fe3+ is iron(III) or ferric ion.• Fe2+ is iron(II) or ferrous ion.

• Hg2+ is mercury(II) or mercuric ion.

• The second ion mercury forms is diatomic:• Hg2

2+ is mercury(I) or mercurous ion.


• Cr3+ is chromium(III) or chromic ion.• Cr2+ is chromium(II) or chromous ion.

• Mn2+ is manganese(II) or manganous ion.• Co2+ is cobalt(II) or cobaltous ion.

• Zinc forms only Zn2+, so it is called zinc ion.• Cadmium forms only Cd2+, so it is called cadmium

ion.• Silver forms only Ag+, so it is called silver ion.


• Polyatomic Ion

• An ion consisting of two or more atoms chemically bonded together and carrying an electrical charge.

• Table 2.5 lists common polyatomic ions.


• What are the names of the following ionic compounds?–BaO–Cr2(SO4)3

BaO is barium oxide.Cr2(SO4)3 is chromium(III) sulfate or chromic sulfate.


• What are the chemical formulas for the following ionic compounds?–potassium carbonate–manganese(II) sulfate

The ions K+ and CO32- form K2CO3

The ions Mn2+ and SO42- form MnSO4


• Binary Molecular Compounds

• A compound composed of only two elements.

• Binary compound of a metal and a nonmetal are generally named using ionic rules.


• Naming Binary Molecular Compounds

• We usually name the elements in the order given in the formula.

• Name the first element using the element name.

• Name the second element using the element root + -ide suffix.


• Add a prefix to each name to indicate the number of atoms of that element. The prefix mono- is used only when needed to distinguish two compounds of the same two elements.

• The final vowel of the prefix is often dropped when followed by an element name that begins with a vowel. Oxygen is the most common example.

N2O4 dinitrogen tetroxide (“a” is dropped)NO nitrogen monoxide (only one “o”)

(also called nitric oxide)


Prefixes (Greek)• One (1) mono-• Two (2) di-• Three (3) tri-• Four (4) tetra-• Five (5) penta-• Six (6) hexa-• Seven (7) hepta-• Eight (8) octa-• Nine (9) nona-• Ten (10) deca-


• Some compounds have common names that differ from their systematic names:

H2S hydrogen sulfide (the “di” is omitted)

H2O water

NH3 ammonia

• Common names need to be memorized.


• Acids and Corresponding Anions

• Oxoacids contain hydrogen, oxygen, and a third central atom.

• To name an acid from its anion name:1.Change an –ate suffix to –ic.2.Change an –ite suffix to –ous.3.Add the word “acid.””

• For example:HNO3 nitric acidH2SO4 sulfuric acid


sulfuric acidH2SO4sulfate ionSO42-

sulfurous acid

H2SO3sulfite ionSO32-

phosphoric acid

H3PO4phosphate ionPO43-

nitric acidHNO3nitrate ionNO3-

nitrous acidHNO2nitrite ionNO2-

carbonic acid

H2CO3carbonateion

CO32-

OxoacidOxoanion


hypochlorous acid

HClOhypochlorite ion

ClO-

chlorous acid

HClO2chlorite ion

ClO2-

chloric acid

HClO3chlorate ion

ClO3-

perchloric acid

HClO4perchlorate ion

ClO4-

OxoacidOxoanion


• What are the names of the following compounds?–OF2

– S4N4

–BCl3

OF2 is oxygen difluoride

S4N4 is tetrasulfur tetranitride

BCl3 is boron trichloride


• What are the formulas for the following binary molecular compounds?– carbon disulfide–nitrogen tribromide–dinitrogen tetrafluoride

The formula for carbon disulfide is CS2.

The formula for dinitrogen tetrafluoride is N2F4.

The formula for nitrogen tribromide is NBr3.


• Bromine has an oxoacid, HBrO2, bromous

acid (compare to HClO2, chlorous acid). What are the name and formula of the corresponding anion?

The anion corresponding to HBrO2 isbromite, BrO2

-.


• Hydrate

• A compound that contains water molecules weakly bound in the crystals.

• The formula of a hydrate is written with a dot before the water molecule(s) included.

• For example:CuSO45H2O


• Hydrates are named using the anhydrous (without water) compound name followed by the prefix for the number of water molecules included and the word “hydrate.”

• For example:CuSO45H2O is named

copper(II) sulfate pentahydrate.


• A compound whose common name is green vitriol has the chemical formula FeSO47H2O. What is the chemical name of this compound?

FeSO47H2O is iron(II) sulfate heptahydrate.


• Calcium chloride hexahydrate is used to melt snow on roads. What is the chemical formula of the compound?

The chemical formula for calcium chloride hexahydrate is CaCl26H2O.

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