Chapter 2Part B

Molecules and Molecular Compounds 2.6

• Only rare gases (8A) naturally found as isolated atoms

• Rest of matter exists as molecules or

ions

Chemical Formulas 2.6

• Diatomic molecules:– H2, O2, N2, F2, Cl2, Br2, I2

Molecular Compounds 2.6

• Compounds composed of molecules with >1 type of atom

Most molecular substances composed of non-metals

Chemical formula

Molecular and Empirical Formulas 2.6

• Molecular formula: Chemical formula with actual number of atoms in a molecule

• Empirical formula: chemical formula with relative number of each type of atom in a molecule (smallest whole number subscripts)

Molecular formula Empirical FormulaC4H10 CH5

H2O H2O

H2O2 HO

Structural Formula 2.6

• 2D:• Shows composition AND attachment of atoms• 3D:• Perspective structural formula

– Uses elemental symbols

• Ball and stick structural formula– Different color = different atom

• Space filing model – Different color = different atom

Ions and Ionic Compounds 2.7

• Typically the nucleus (+ and °) is unchanged by chemical reactions

• Gain or loss of electrons (-) produces:– CATions + loss of electrons– ANions – gain of electrons

Formation of a Cation 2.7

Na: atomic number 11 Na+: 11 protons and 10 electrons = loss of 1 electron

Formation of an Anion 2.7

Cl: atomic number 17 Cl-: 17 protons and 18 electrons = loss of 1 electron

Generally 2.7

• Metals - electron cations• Nonmetals + electron anions• Therefore ionic compounds are

metal:nonmetal

• *Chemical properties of ions are very different from chemical properties of parent atom (just from the loss of a few – charges)*

Why Do Atoms Ionize? 2.7

• Atoms prefer to gain/lose electrons in order to have the same amount of electrons as their nearest noble (inert) gas– = stability!

Simple Ion Rules 2.7

Ionic Compounds 2.7• Cations + anions• Metal element + non-metal element• (Metal ion + non-metal ion)• Very strong chemical bond• Must be electrically neutral formula

– Careful with charges and subscripts!

Nomenclature of Inorganic Compounds 2.8

• 50,000,000 + chemical substances known!– Therefore only some have common names

Therefore we have a system for naming…

– *memorizing and naming PRACTICE are only way*

Inorganic Compounds-Cations 2.8

– 1—Cations: name of metal atom + ion• A. One cation only: Al3+ = aluminum ion

– *Metals from groups IA, IIA, Al, Ag+ and Zn2+*

• B. several cations: Fe2+ = iron (II) ion; ferrous ion

(different properties)Fe3+ = iron (III) ion; ferric ion– *typically transition metals*

Inorganic Compounds-Cations (cont) 2.8

– C. cation formed from nonmetal atoms• NH4

+ ammonium ion

• H3O+ hydronium ion

Anions 2.8

• 2--anions:

(A. Mono and some polyatomic)

(B. Most polyatomic)

1 23 4

Oxyanions (cont) 2.8

3 O atoms

4 O atoms

Oxyanions (cont) 2.8

– C. add H+ to oxyanion: add hydrogen to anion name

Common Anions 2.8

Ionic Compounds 2.8

• 3. Ionic Compounds: cation name + anion name– NaCl sodium chloride

– AgNO3 silver nitrate

Acids 2.8• *recognize since typically contain H as first

element in compound*• * it is similar to an ionic compound with H+

as the cation joined to some anion*• 1

2

3

Binary Molecular Compounds 2.8

• * 2-element molecular compounds* • *naming is similar to naming ionic compounds*

• RULES:– 1—element closest to metals is written first

• *exception: compound contains O + Cl, Br or I?• O written last

– Cl2O = dichlorine monoxide

– 2—both elements in same group?• Lower one named first

– 3—name of second element ends in –ide• NF3 = nitrogen trifluoride

– 4—Greek prefixes used to indicate number of atoms on each element (mono not used with first element)

• Cl2O = dichlorine monoxide

2.8

Organic Compounds 2.9• *Can contain C,H,O,N*• Alkanes: contain only H and C; simplest

class

– 1C:4other atoms

Organic Compounds (cont) 2.9

• Alkane derivatives:– replace H with functional grp

• OH=alcohol

–Isomers: same chemical

– formulas but different arrangements of atoms

• describe key experiments that led to the discovery of electrons and the nuclear model of the atom

• understand and explain Dalton’s atomic theory including Law of Multiple Proportions

• describe atomic structure• describe electrical charge and relative masses of +,

and –• be able to use chemical symbols, atomic number and

mass number to express the subatomic composition of elements and their isotopes

• be able to calculate atomic weight from atomic masses and isotope abundances

• describe the organization of elements in the periodic table, including:

• periods and groups• metals, non-metals and metalloids• group names and characteristics

Learning Goals

• explain how ions are formed and be able to use the periodic table to predict the charges of common ions

• distinguish between molecular substances and ionic substances

• distinguish between molecular and empirical formulas

• be able to write molecular, structural and ionic formulas as well as binary inorganic compounds and acids from names and vice versa

• ID organic compounds and name simple alkanes and alcohols