Chapter Two:

Atoms, Molecules & Ions

Atomic Theory & Structure

Isotopes, Numbers & Masses

Periodic Table

Molecules, Ions, Compounds & Formulas

Naming Species

Atomic Theory and StructureWhat is the smallest piece of matter possible?

Democritus called the smallest particles “atomos”

Dalton’s atomic theory of matter: elements are composed of small particles -- atoms all atoms of an element are identical atoms are not created or destroyed chemically compounds formed by chemical combination of two or more elements a given compound has same relative number & type of atoms (law of constant composition) atoms retain character during chemical rxns. only undergo rearrangement (conservation of matter)

Law of Multiple ProportionsIf two elements, A & B, form more than one

compound, the masses of B that can combine with a given mass of A are in a ratio of small whole numbers

C

C O

O O12 g of Carbon & 32 g of Oxygen

12 g of Carbon & 16 g of Oxygen

2 x

carbon dioxide

carbon monoxide

Subatomic Particles-J.J. Thompson determined charge:mass ratio of e-, 1897-Robert Millikan measured charge of e-, 1909-Thompson developed “plum pudding” model of atom-Rutherford developed “nuclear” model of atom

alpha particle source

detector

Modern Atomic Structure

PARTICLE CHARGE* MASS (AMU)

Proton +1 1.0073

Neutron 0 1.0087

Electron -1 5.486 x 10-4

* unit charge = 1.602 x 10-19 C (coulomb)

amu (u) -- atomic mass unit = 1.66054 x 10-24 g

Atomic Numbernumber of protons in an atomdefines an elementshown as the symbol subscript 6C

Mass Numbertotal number of protons plus neutronswill vary between isotopesshown as the symbol superscript12C

Isotopeselements which have the same atomic number but different mass numbers12C6 13C6 14C6 are isotopes

Periodic Table–Allows for organization of elements

–Allows for grouping of elements in terms of physical and chemical characteristics

Metals, Non-metals & Metalloids

–Group 1A Alkali Metals

–Group 2A Alkaline Earth Metals

–Group 6A Chalcogens

–Group 7A Halogens

–Group 8A Nobel Gases

–B Groups Transition MetalsKnow these !!

Molecules and Molecular Compounds

•Molecule — the smallest particle of a compound that can be identified as that compound

— chemical combination of two or more atoms

— a pure substance

• Chemical Formula— a symbol representation of a molecule/compound— shows the type and ratio of atoms in a molecule

type is given by symbolratio is given by a subscript to right of symbol

Examples:

H2O

H2O2

CO2

CO

O2

Molecule Ratio

2 : 1

2 : 2

1 : 2

1 : 1

-

heteroatomic

heteroatomic

heteroatomic

heteroatomic

homoatomic

• Formulas

—Molecular Formulas Give the type and exact number of each type

of atom

—Empirical Formulas Give only the type and simplist ratio of

atoms

H2O

H2O2

C6H6

C2H6

Molecular Formula Empirical Formula H2O

HO

CH

CH3

— Structural Formulas Show which atoms are attached to which

atoms

C2H6O

H C O C H

H

H H

H

H C C O H

H

H

H

H

dimethylether

ethanol

Ions & Ionic Compounds

• Some elements will either lose or gain one or more electrons to become charged species

• Metals– typically lose electrons, become +, cations

• Non-Metals– typically gain electrons, become -, anions

Monatomic Ions– made from a single element

• Na Na+ + 1e-

• Cl + 1e- Cl-

Na Na+1e- +

Cl Cl- + 1e-

11 p+ 11 e-

11 p+ 10 e-

17 p+ 18 e-

17 p+ 17 e-

Hints to Determine Ion Charges

• Hydrogen +1

• Oxygen - 2

• Group IA +1

• Group IIA +2

• Group VIA - 2

• Group VIIA - 1

Polyatomic Ions -- “molecules” which have a net positive or negative charge

– CO32- carbonate ion

– NH4+ ammonium ion

– OH- hydroxide ion

Prediction of Charges -- all species tend toward the most stable state

– Nobel gases are very stable– Elements add or lose electrons to “mimic” nobel gases

Ionic Compounds

• Oppositely charged ions form ionic compounds

– held together by ionic bonds due to the

electrostatic attraction between the

opposite charges

• Ionic compounds are always neutral species

• Mg2+ and Cl- form MgCl2 not MgCl

or Mg2Cl

Naming Inorganic Compounds

• Names of Monatomic Ions

– cations are named for the elements Na+ is sodium ion Al+3 is aluminum

ion Fe+2 is iron(II) ion Fe+3 is iron(III) ion (ferrous ion) (ferric ion) Cu+ is copper(I) ion Cu2+ is copper(II)

ion (cuprous ion) (cupric ion)

– anions are named for the root name of the element with the ending -ide

O-2 is oxide ion Cl- is chloride ion H- is hydride ion N-3 nitride ion

•Naming Polyatomic Ions

• Know the names, charges and formulas of the important polyatomic ions

– NH4+ ammonium ion

– CO3-2carbonate ion

– SO4-2 sulfate ion– OH- hydroxide ion

– NO3- nitrate ion

• Polyatomic ions are treated as separate entities or units

• Naming and formula rules are the same as for compounds with monatomic ions

Naming Binary Ionic Compounds

• Cations always named first• Anions always named last

– NaCl sodium chloride

– BaCl2 barium chloride

• for cations which have more than one possible charge, the charge of the ion must be given in the name– Fe2O3 iron(III) oxide– FeO iron(II) oxide

• Combinations must be neutral!

• Examples:

– 2 Na+ and 1 CO3-2 is sodium carbonate

Na2CO3

– 2 NH4+ and 1 S-2 is ammonium sulfide

(NH4)2S– 1 Ba+2 and 2 OH- is barium hydroxide

Ba(OH)2

– 3 Mg+2 and 2 PO4-3 is magnesium

phosphate Mg3(PO4)2

– 1 Na+ , 1 H+ and 1 CO3-2 is sodium hydrogen

carbonate or sodium bicarbonate, NaHCO3

Acids

• A compound that produces hydrogen ions (H+) when dissolved in water

• tastes sour• turns litmus red• has a pH less than 7• typically the formula begins with one or

more H’s– HCl(aq) hydrochloric acid

– H2SO4(aq) sulfuric acid

– HC2H3O2(aq) acetic acid

Binary Acids

• Acids which contain H and another non-metallic element

• Naming -- to the root name of the non-metallic element:– add the prefix hydro-– add suffix -ic acid

• HF(aq) hydrofluoric acid

• HBr(aq) hydrobromic acid

• HCl(aq) hydrochloric acid

Note!

Oxyacids

• Acids which contain H and O and another element (or H and a polyatomic anion containing O)

• Naming -- to the polyatomic ion name– if the suffix is -ate, change it to -ic

– if the suffix is -ite, change it to -ous

– add acid to the end of the name• HNO3 nitric acid HNO2 nitrous acid

• H2SO4 sufuric acid H2SO3 sulfurous acid

• You must know polyatomic ion names/charges

Binary Molecular Compounds

• Chemical combinations of non-metals and non-metals (no ions involved)

• The more metallic element is named first• The second element (less metallic) is named

with the ending -ide• Because there are no ions to use to

determine relative ratio of atoms we must indicate the number of each atom by a prefix– N2O3 dinitrogen trioxide– SO3 sulfur trioxide

Name the Following:

• CaI2

• Cu2O

• CuO

• Cl2O7

• HClO3

calcium iodide

copper(I) oxide

copper(II) oxide

dichlorine heptaoxide

notechloric acid

Write Formulas for the Following:• calcium hypochlorite

• Mg+2 and ClO2-

• carbon tetrachloride

• NH4+ and SO4

-2

Ca(ClO)2

Mg(ClO2)2

CCl4

(NH4)2SO4