Ch. 3: Molecules, Ch. 3: Molecules, Compounds, and Chemical Compounds, and Chemical

Equations (Part I)Equations (Part I)

Dr. Namphol Sinkaset

Chem 200: General Chemistry I

I. Chapter OutlineI. Chapter Outline

I. IntroductionII. Naming “Type I” CompoundsIII. Naming “Type II” CompoundsIV. Polyatomic IonsV. Acid NamesVI. Naming “Type III” CompoundsVII. Molecular Masses

I. Chemical FormulasI. Chemical Formulas

• There are three types of formulas. molecular: gives the actual

number of atoms of each element in a molecule of a compound (e.g. H2O2)

empirical: gives the relative number of atoms of each element in a compound (e.g. HO)

structural: uses lines to represent covalent bonds and shows interconnectivity

I. Chemical ModelsI. Chemical Models

• Formulas lead to models which give an idea of the 3-D shape of a molecule.

I. Breakdown of Pure SubstancesI. Breakdown of Pure Substances

I. Chemical NomenclatureI. Chemical Nomenclature

• Like any specialized field, chemistry has its own language.

• The ability to name and recognize names of chemical entities is very important.

• The naming system is LOGICAL!!• The periodic table is indispensable

when you are first learning nomenclature.

II. Type I CompoundsII. Type I Compounds• Type I compounds are ionics that have a

metal from Groups 1 or 2 and a nonmetal from Groups 14-17.

• Examples: NaCl = sodium chloride MgBr2 = magnesium bromide

K2S = potassium sulfide

II. Type I CompoundsII. Type I Compounds

• To get a formula from a name, remember that a compound must be neutral.

• Ion charges can be found by locating the element on the periodic table.

• “The charge on one becomes the subscript of the other.”

II. Type I CompoundsII. Type I Compounds

• e.g. What are the formulas for sodium nitride, calcium chloride, potassium sulfide, and magnesium oxide?

III. Transition MetalsIII. Transition Metals

• Transition metals are found in the “Valley,” Groups 3-12, of the periodic table.

• Transition metal cations often can carry different charges, e.g. Fe2+ and Fe3+.

• Thus, a name like “iron chloride” is ambiguous.

III. Type II Compounds III. Type II Compounds

• Type II compounds are ionics that have a transition metal (Groups 3-12) and a nonmetal (Groups 14-17).

• Examples: FeCl2 = iron(II) chloride

FeCl3 = iron(III) chloride

III. Type II CompoundsIII. Type II Compounds

• e.g. Give the correct name or formula for the compounds below.

a) MnO2

b) copper(II) chloride

c) AuCl3d) molybdenum(VI) fluoride

e) Hg2Cl2

III. Type II CompoundsIII. Type II Compounds

• An archaic naming system uses common names for transition metal cations of different charge. Higher charge given –ic suffix Lower charge given –ous suffix

• FeCl3 = ferric chloride

• FeCl2 = ferrous chloride

III. Some Transition Metal CationsIII. Some Transition Metal Cations

IV. Additional ComplicationsIV. Additional Complications

• To make naming ionic compounds harder, sometimes polyatomic ions are involved.

• polyatomic ion: two or more atoms that are bonded covalently and have a net positive or negative charge

IV. Common Polyatomic IonsIV. Common Polyatomic Ions

• These can be involved in either Type I or Type II compounds.

• Polyatomic ions containing oxygen are called oxoanions.

IV. Oxoanion FamiliesIV. Oxoanion Families

• There are families of oxoanions, and they have a systematic naming system.

• Have either two- or four-member families. e.g. NO2

- and NO3-

e.g. ClO-, ClO2-, ClO3

-, and ClO4-

IV. Two-Member FamiliesIV. Two-Member Families

• For a two-member family, oxoanion with fewer O atoms is given the “–ite” suffix while the one with more O atoms is given the “–ate” suffix. e.g. NO2

- = nitriteand NO3

- = nitrate

IV. Four-Member FamiliesIV. Four-Member Families

• For the four-member families, the prefixes “hypo-” and “per-” are used to indicate fewer or more oxygen atoms.

• e.g. the chlorine oxoanions ClO- = hypochlorite ClO2

- = chlorite

ClO3- = chlorate

ClO4- = perchlorate

IV. Oxoanion Naming IV. Oxoanion Naming SummarySummary

IV. Naming PracticeIV. Naming Practice

• e.g. Give names or formulas for the following compounds.

a) Na2CO3

b) magnesium hydroxide

c) potassium nitrate

d) CoPO4

e) nickel(II) sulfate

f) NaClO2

V. AcidsV. Acids

• Acids are special ionic compounds that have H+ as the cation.

• There are two categories of acids that have different naming rules.

1) Binary acids

2) Oxoacids

V. Naming Binary AcidsV. Naming Binary Acids

• Binary acids are comprised of H+ and a nonmetal anion. HCl = hydrochloric acid HBr = hydrobromic acid H2Se = hydroselenic acid

HI = hydroiodic acid

• So what’s the naming rule?

V. Naming OxoacidsV. Naming Oxoacids

• Set 1 HNO3 = nitric acid

H2SO4 = sulfuric acid

HClO3 = chloric acid

HClO4 = perchloric acid

H2CO3 = carbonic acid

H3PO4 = phosphoric acid

• Set 2 HNO2 = nitrous acid

HClO2 = chlorous acid

HClO = hypochlorous acid H2SO3 = sulfurous acid

Oxoacids are comprised of H+ and an oxoanion.

So what’s the naming rule?

VI. Type III CompoundsVI. Type III Compounds

• Type III compounds are covalent (nonmetal bonded to nonmetal).

• Naming rules:1) Element w/ lower group # is named 1st using the

normal element name EXCEPT when halogens are bonded to oxygen.

2) If elements are in the same group, lower element named first.

3) Second element is named using its root and the “-ide” suffix.

4) #’s of atoms indicated with Greek prefixes EXCEPT when there is only one atom of the first element.

VI. Greek PrefixesVI. Greek Prefixes

VI. Type III CompoundsVI. Type III Compounds

• Some examples: ClO2 = chlorine dioxide

N2O5 = dinitrogen pentoxide

S2Cl2 = disulfur dichloride

SeF6 = selenium hexafluoride

VI. Naming PracticeVI. Naming Practice• e.g. Give the correct formula or name of the

compounds below.a) CoCl3b) dichlorine heptaoxidec) SrOd) magnesium hydroxidee) carbon tetrachloridef) HFg) sodium hydride

h) V2O5

i) Ru(ClO4)3

j) hydrosulfuric acid

k) H2SO4

l) titanium(IV) oxide

m) N2F2

VII. Masses of Compounds VII. Masses of Compounds

• Atomic masses are readily accessible via the periodic table, e.g. H = 1.008 amu.

• Molecular masses or molecular weights are calculated by adding up the masses of each atom in the compound.

• Thus, molecular mass = sum of atomic masses.

VII. Molecular Mass of WaterVII. Molecular Mass of Water

• The formula for water is H2O, so it is comprised of 2 H atoms and 1 O atom.

VII. Formula MassVII. Formula Mass

• e.g. What is the formula mass of barium nitrate?