Atoms, Molecules, and Ions

1
Atoms, Molecules, and Ions

• Chapter 2

2
Early Observations of Matter- early 1700s

• Lavoisier - Conservation of Matter
• Careful measurements showed that mass is neither
  created nor destroyed in a chemical reaction.
• Proust - Definite Proportions (composition)
• A given compound always contains exactly the same
  proportion of elements by weight.

3
Atomic Theory- ca. 1800
mass of Oxygen reacting w/ 1 g of Carbon
I 1.33 g II 2.66 g

• John Dalton - law of multiple proportions
• When elements form a series of compounds, the
  ratio of the masses of the second element can
  always be reduced to whole numbers.

4
A New System of Chemical Philosophy

• John Dalton - 1808
• Each element is made up of tiny particles called
  atoms.
• Atoms of a given element are identical.
• Compounds are formed when atoms combine with one
  another.
• Chemical reactions involve reorganization of the
  atoms - changes in the way they are bound
  together.

5
Relative Molecular Masses
6
The Electron Part I

• J.J. Thompson - 1897
• Cathode rays can be deflected by electric and
  magnetic fields.
• The charge-to-mass ratio of an electron can be
  determined.
• 1.76 x 108 C/g

7
The Electron Part II

• Robert Milikan - 1909
• Charged oil droplets will fall at integral rates
  between two charged plates.
• The charge on the electron is 1.60 x 10-19C.

1.60 x 10-19 Coul
9.09 x 10-28 g
Mass
1.76 x 108 Coul/g
8
Modern Atomic Structure

• The magnitude of the charge on the electron and
  proton is the same.

9
The Common Atom
10-10 m
10-15 m
atomic number
3

• Li

element symbol
mass number
7
10
Isotopes

• The number of neutrons can vary within any given
  element.
• 6Li, 7Li
• 11C, 12C, 13C

11
Ions

• The number of electrons in any given element is
  also not constant.
• Na vs. Na
• Cl vs. Cl-
• Fe or Fe or Fe2 or Fe3

12
Atomic Weights

• Calculate the atomic weight of boron, B, from the
  following data
• ISOTOPE ISOTOPIC MASS (amu)
  FRACTIONAL ABUNDANCE
• B-10 10.013
  0.1978
• B-11 11.009 0.8022

13
Atomic Weights

• Calculate the atomic weight of boron, B, from the
  following data
• ISOTOPE ISOTOPIC MASS (amu)
  FRACTIONAL ABUNDANCE
• B-10 10.013
  0.1978
• B-11 11.009 0.8022
• B-10 10.013 x 0.1978 1.9805
• B-11 11.009 x 0.8022 8.8314
• 10.8119 10.812
  amu
• 
  ( atomic wt.)

14
Nomenclature of Ions - Type I

• Cations X
• Use the name of the element.
• Anions X-
• Add -ide to the root of the element name.
• Binary Compounds
• Name cation first, followed by the anion.

15
Naming Binary Compounds

• NaF -
• LiCl -
• MgO -

16
Naming Simple Compounds

• NaF - Sodium Fluoride
• LiCl - Lithium Chloride
• MgO - Magnesium Oxide

17
Nomenclature of Ions - Type II

• Cations
• Specify charge on metal ions - Fe(II), Cr(II)
• or
• Use -ic for highest charge and -ous for lowest
  charge
• Fe(II) - Ferrous Chloride
• Fe(III) - Ferric Chloride

18
Nomenclature of Ions - Type II

• Polyatomic anions
• If only one element is involved use -ide
• O22- - peroxide, N3- azide
• or
• Simple mixed element ions
• OH- - Hydroxide
• CN- - Cyanide

19
Oxoanions

• Polyatomic ions with a varying number of oxygen
  atoms
• ClO- - Hypochlorite
• ClO2- - Chlorite
• ClO3- - Chlorate
• ClO4- - Perchlorate

Use these two if only two oxoanions exist.
20
More Practice

• Na2SO4 OR Na2SO3
• Sodium Sulfate Sodium Sulfite
• AgCN OR Cd(OH)2
• Silver Cyanide Cadmium Hydroxide
• Ca(ClO)2 OR K2(ClO4)
• Calcium Hypochlorite Potassium Perchlorate

21
Ions You Should Know

• NH4 - Ammonium
• OH- - Hydroxide
• CN- - Cyanide
• SO42- - Sulfate
• ClO42- - Perchlorate

• O22- - Peroxide
• PO43- - Phosphate
• CO32- - Carbonate
• HCO3- - Bicarbonate

22
Chemical Equations

• Balance the following equation. SbCl5
  H2O SbOCl3 HCl

Reactants
Products
23
Chemical Equations

• Balance the following equation. SbCl5
  H2O SbOCl3 2 HCl

24
Chemical Equations

• Balance the following equations.
• Mg SiO2 MgO Si
• CaCl2 Na2CO3 CaCO3 NaCl
• C6H6 O2 CO2 H2O
• Al2S3 H2O Al(OH)3 H2S

25
Chemical Equations

• Balance the following equations.
• 2 Mg SiO2 2 MgO Si
• CaCl2 Na2CO3 CaCO3 2 NaCl
• 2 C6H6 15 O2 12 CO2 6 H2O
• Al2S3 6 H2O 2 Al(OH)3 3 H2S