Chapter 2
The Periodic Table
and Some Properties
of the Elements
Read all of Chapter 2
2.1 Differentiate between an
element, a compound, and a
mixture using Dalton’s Atomic
Theory. [Readings 2.1 Review
Questions 1 – 8]
Elements, Compounds, &
Mixtures
• Many compounds can undergo a chemical
decomposition resulting in two or more
simpler substances.
• Substances which can’t be decomposed any
further are elements
• 90 elements exist naturally
• 23 elements have been made in the lab
1
Decomposition of HgO
Copyright 2000 John Wiley and Sons, Inc.
Copyright 2000 John Wiley and Sons, Inc.
HgO is red solid in tip of
glass tube.
Copyright 2000 John Wiley and Sons, Inc.
Heating decomposes HgO
to form liquid mercury
drops at top of tube and
gaseous oxygen.
Drop of mercury condensed
at bottom of tube in ice bath.
Compounds and Elements
Copyright 2000 John Wiley and Sons, Inc.
Heating decomposes HgO
to form liquid mercury
drops at top of tube and
gaseous oxygen.
Element - a substance that cannot be decomposed into
simpler substances by chemical reactions.
Mercury - Hg
Oxygen - O2
Compound - a substance formed from two or more
elements with elements combined with fixed
proportions by mass. HgO
Compounds
• Compounds are formed of two or more
elements
• The elements are always present in a fixed
proportion by mass
• e.g. water is always 8 parts oxygen and 1
part hydrogen by mass
• The properties of a compound differ from
the properties of its elements
2
Mixtures
• Mixtures can have variable composition.
• A sand/water mixture can have varying
amounts of sand
• Homogeneous vs. heterogeneous mixtures
– Homogeneous - the same properties throughout
the sample e.g. brass
– Heterogeneous - different properties e.g. oil and
vinegar
Pure Substances and Mixtures
Michael Watson
Michael Watson
Iron and sulfur
(pure substances)
Mixture of iron
and sulfur
Separation of iron
and sulfur mixture
with a magnet.
Pure substance - composition always the same
Mixture - combination of two or more pure substances
which may have variable composition
Classification of Matter
Mixture Any matter consisting of two or more substances
combined in no particular proportion by mass.
Pure Substance An element or a compound.
3
Dalton’s Atomic Theory
• The “Cheese Atom”
• The Law of Conservation of Mass
– There is no gain nor loss of mass in a chemical
reaction
• 2 CH3OH + 3 O2 ––> 2 CO2 + 4 H2O
64g
+ 96g
160g
88g
=
+ 72 g
160 g
Dalton’s Atomic Theory
• The Law of Definite Proportions
• Carbon dioxide forms from the reaction of
oxygen with carbon
• 1.000 g of carbon will react with 2.664 g of
oxygen in forming carbon dioxide
• This ratio is constant always for CO2
Dalton’s Atomic Theory
• Matter consists of atoms
• Atoms are indestructible (in a chem rxn)
• All atoms of an element are have identical
properties
• Atoms of different elements differ in mass
& properties
• Atoms combine to form a compound of a
fixed mass ratio
4
Law of Multiple Proportions
Whenever two elements form more than one compound,
the different masses of one element that combine with
the same mass of the other element are in the ratio of
small whole numbers.
SO2 Sample Sulfur Oxygen
Mass
Mass
Mass
--------- --------- --------SO2 4.50 g 2.25 g 2.25 g
SO3 5.73 g 2.25 g 3.38 g
2.25/3.38 = 2/3
Copyright 2000 John Wiley and Sons, Inc.
2.2 State the name and symbol
for elements and compounds.
Read simple chemical equations
[Readings 2.3 Review Questions
2.9, 10, 12, 13, 16, 21, 22, & 23 ]
Elemental Symbols
• Each element has a unique symbol
• The first letter is always capitalized
• The second letter, if present, is always
lower case
• Carbon is symbolized by C
• Bromine is symbolized by Br
• Most symbols come from the compound
name
5
Names and Symbols
•
•
•
•
•
•
•
Oxygen
Fluorine
Aluminum
Chlorine
Zinc
Silicon
sulfur
Names and Symbols
•
•
•
•
•
•
•
Oxygen
Fluorine
Aluminum
Chlorine
Zinc
Silicon
Sulfur
O
F
Al
Cl
Zn
Si
S
Names and Symbols
•
•
•
•
•
•
•
•
Diatomic molecules
Hydrogen
H2
Nitrogen
N2
Oxygen
O2
Fluorine
F2
Chlorine
Cl2
Bromine
Br2
Iodine
I2
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Chemical Formulas
Compounds & Elements pure substances with fixed
compositions
Chemical Formulas - show
elements present in a compound
or element with chemical symbol
and number of each element
with subscripts
CuSO4• 5H2O - blue solid
CuSO4 - white solid
X nH2O -hydrate
Examples - H2 , H2O, H2O2 ,
CH3OH, Fe(NO3)2 • 6H2O,
Fe(NO3)3 • 6H2 O, Fe(NO3 )3
Chemical Equations
2H2 + O2
2H2O
Chemical Equation
Species reacting
Species Formed
Copyright 2000 John Wiley and Sons, Inc.
Reaction in main rocket
engine of space shuttle
Subscripts - number of atoms
of element in compound
Coefficients - number of each
compound in reaction
P4(s) + 6 Cl2(l)
Copyright 2000 John Wiley and Sons, Inc.
4 PCl3(s)
Reactants - phosphorous (P4)
chlorine (Cl2)
Product - phosphorous trichloride (PCl3)
P4 - purple model
Cl2 - green model
Copyright 2000 John Wiley and Sons, Inc.
PCl3 - models for
compound formed
Click picture to view movie.
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2 Na(s) + Cl2(g)
Copyright 2000 John Wiley and Sons, Inc.
2 NaCl(s)
Reactants - sodium (Na)
chlorine (Cl2)
Product - sodium chloride
(NaCl)
Na - silver spheres
Cl2 - green double spheres
Copyright 2000 John Wiley and Sons, Inc.
NaCl - 3D pattern of
alternating Na+ & Cl-
Click picture to view movie.
2.3. Determine the relative and
average weights of an element
[Readings 2.4 - 2.5 Review
Problems ]
Weights on the Periodic Table
Average Weights
Relative Weights
C is defined as weighing 12 AMU
8
ATOMIC MASSES
MASS SPECTROMETER
ION ACCELERATING
FIELD
POSITIVE
IONS
SAMPLE
HEATER VAPORIZES
SAMPLE
1/3
ATOMIC MASSES
MASS SPECTROMETER
ION ACCELERATING
FIELD
POSITIVE
IONS
ACCELERATED
ION BEAM
MAGNETIC
FIELD
2/3
ATOMIC MASSES
MASS SPECTROMETER
DETECTOR
LEAST MASS
ACCELERATED
ION BEAM
MOST MASS
MAGNETIC
FIELD
MASS O
MASS
12C
= 1.33333333
3/3
9
Weights on the Periodic Table
Average Weights
Relative Weights
C is defined as weighing 12 AMU
1 H atom weighs 1/ 12 times 1 C atom
1 O atom is 16/12 the weight of 1 C atom
2.4. Determine the subatomic
structure of atoms, ions, and isotopes.
Use AZ X charge notation.
[Readings 2.5 Review Problems 32,
33, 134, & 135]
Subatomic Particles
Figure not drawn to scale
since nucleus is 10-5 the size
of atom. Most of space of
atom is occupied by electrons
Particle
-----------------Electron
Proton
Neutron
Mass (g)
Electrical Charge
-------------------- -------------------9.1094 x 10-28
11.6726 x 10-24
1+
1.6749 x 10-24
0
10
Subatomic Particles
particle charge
mass
Nuclear:
Protons + 1.67x10-24g 1amu
Neutron ± 1.67x10-24g 1amu
Extranuclear:
Electron - 9.11 x 10-28 0amu
___________________________________
Diameter of Atom:
≈ 10-8cm
Diameter of nucleus: ≈ 10-13cm
Subatomic Structure
Elements can be represented symbolically:
A
Z
X charge
Subatomic Structure
Elements can be represented symbolically:
A=Z+N
Mass #
Z = # of protons
N = # of Neutrons
A
Z
X charge
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Subatomic Structure
Elements can be represented symbolically:
A
Z
X charge
Z = # of protons
Atomic #
Subatomic Structure
Elements can be represented symbolically:
A
Z
X charge
X = element
Subatomic Structure
Elements can be represented symbolically:
A
Z
X charge
charge = Z - e
e = # of electrons
12
Subatomic Structure
Elements can be represented symbolically:
A=Z+N
Mass #
Z = # of protons
N = # of Neutrons
A
Z
X charge
charge = Z - e
e = # of electrons
X = element
Z = # of protons
Atomic #
Examples
40
20 Ca
20 protons
20 neutrons
20 electrons
42
20 Ca
20 protons
22 neutrons
20 electrons
40
+2
20 Ca
20 protons
20 neutrons
18 electrons
Examples
40
20 Ca
20 protons
20 neutrons
20 electrons
42
20 Ca
20 protons
22 neutrons
20 electrons
40
+2
20 Ca
20 protons
20 neutrons
18 electrons
Isotopes
13
Examples
40
20 Ca
20 protons
20 neutrons
20 electrons
42
20 Ca
20 protons
22 neutrons
20 electrons
40
+2
20 Ca
20 protons
20 neutrons
18 electrons
Isotopes
Ion
2.5. Determine the average mass of
an element, given the mass and
percent abundance of the isotopes.
[Readings 2.4 Problems 2.132 & 140
Isotopes
35
37
Cl-
Cl-
•
•
•
•
75.5%
17 protons
18 neutrons
18 electrons
•
•
•
•
24.5%
17 protons
20 neutrons
18 electrons
• Average Mass 35.5 amu
14
Sample Problem
• Copper exists as two isotopes, copper 63
and copper 65 with a percent abundance of
69.09% and 30.91% respectively. Calculate
the average mass of copper if the mass of
Cu 63 is 62.93amu and Cu 65 is 64.93.
2.6. Characterize the parts of the
Periodic Table
[Readings 2.6 - 2.7 Problems
2.34, 36, 37, 42, 47, 53, 54, &
57]
Periodic Table
15
Periodic Table - Extended Form
Representative elements - orange boxes
Transition metals - cream boxes
Inner transition metals - green boxes
Lanthanide elements - elements 58-71
Actinide elements - elements 90-103
Metals, Nonmetals, and Metalloids
Nonmetallic Elements
Match the nonmetallic elements shown in this
picture with their names and formulas:
bromine (Br2), chlorine (Cl2), graphite (C),
iodine (I2), phosphorus (P4), and sulfur (S8)
16
2.7. Distinguish between
molecular and ionic compounds.
Predict the charges on ions and
write the correct formula for
ionic compounds. [Readings 2.8
- 2.10 Problems 2.59, 61, 64, 67,
70, 71, 73, 74, 76, & 81]
Molecular and Ionic Compounds
Copyright 2000 John Wiley and Sons, Inc.
Molecular compounds - fundamental particles
are discrete molecules such a water, H2O
Ionic compounds - fundamental particles are
ions arranged in 3D array such as shown for
sodium chloride, NaCl
Formation of Molecular Compound
Click on pictures to view movies.
P4(s) + 6 Cl2(g)
4 PCl3(l)
Discrete molecules of phosphorous trichloride,
PCl3, are formed by reacting solid phorphorous
with chlorine gas.
17
Formation of Ionic Compound
Click on pictures to view movies.
2 Na(s) + Cl2(g)
2 NaCl(s)
Na+ ions and Cl- ions are formed by the transfer of an electron from a Na atom to a chlorine
atom of Cl2. The resulting ions arrange themselves in a 3D array of alternating charged ions.
Cleaving and Ionic Crystal
An ionic crystal such as sodium chloride will shatter
if struck with a hammer. However, if the hammer is
used to tap a razor blade set on the crystal, the crystal
will be cleaved into two pieces when the blade is
aligned properly.
Conductivity Tester
Click picture to
view operation of
conductivity tester
Apparatus consists of 25 watt and 100 watt light
bulbs wired in parallel in 120 volt AC circuit
with two open leads inserted into test solution.
Strong electrolytes light both bulb, weak electrolytes
only the 25 watt bulb and nonelectrolyte neither.
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Ionic Charges
IA
Li
+
Na+
+
IIA
IIIA
2+
IVA
4–
Be
C
Mg2+ Al3+
Si 4–
VA
N
3–
P 3–
2+
VIA
O
2–
S 2–
2–
VIIA
F–
Cl –
Br –
K
Ca
Se
Rb+
Sr2+
Te 2– I –
Cs+
Ba2+
Ionic Compound Formulas
• Cation is listed first
• The subscripts in a formula are used to
produce an electrically neutral formula
unit
• The subscripts give the smallest whole
number set
• ex. calcium nitride
Ionic Compound Formulas
• Transition and Post-transition Metals (Type
II metals)
• Most form 2 or more charge states
• Fe2+ and Fe3+ or Pb2+ and Pb4+
• Write the formula for:
– a Cr3+ - fluoride compound
– a Au+ - sulfide compound
19
Polyatomic Ions
•
•
•
•
•
•
•
•
SO42SO32NO3–
NO2–
ClO3–
ClO2–
ClO –
ClO4–
•
•
•
•
•
•
•
•
Sulfate
Sulfite
Nitrate
Nitrite
Chlorate
Chlorite
Hypochlorite
perchlorate
Polyatomic Ions
• Memorize the name, formula, and charge of
each ion in table 2.6, p. 76
• ite vs ate
• The chlorate series
• Nomenclature using polyatomic ions
• Write the formula of calcium nitrite,
calcium nitrate, and calcium nitride
2.8. Given a structure or formula,
provide the correct compound
name and vv. [Readings 2.10 2.11 Problems 2.104, 105, 108,
110, 112, 113, 115, & 116]
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Naming Organic Compounds
• Compounds of carbon
• Alkanes (counting carbons)
– Meth - 1
– Eth
-2
– Prop - 3
– But
-4
– Pent - 5
– Hex - 6
– Hept, oct, non, dec 7,8,9,10
Naming Organic Compounds
• Alkanes
– CnH2n+2
– methane - n = 1 ==> CH4
– ethane
n = 2 ==> C2H6
– propane n = 3 ==> C3H8
CH3 CH3
CH3 CH2 CH3
H H
H C
C H
H H
Naming Ionic Compounds
• Binary Ionic Compounds
• Cation name is first e.g. Na+ is sodium
• Anion is named second
– The stem is used followed by “ide”
– e.g. O 2- is called oxide
– S 2- is sulphide
• Na2O is called sodium oxide
21
Practice
• Fill in the following table by providing the
missing information
CaH2
_____________
_____________ Potassium sulfide
AlBr3
_____________
_____________ Lithium nitride
Stock System of Naming
•
•
•
•
Transition and post-transition metals
Metals with multiple charges
The charge is specified by roman numerals
FeCl2
– The iron is Fe2+ thus iron(II)
• iron(II) chloride
• FeCl3 is named?
Stock System of Naming
• Fill in the following table
Cr2S3
______________
SnF2
______________
______________ Tin(IV) chloride
______________ Lead(II) nitride
22
Binary Compound – Two
Nonmentals
• mono = 1 (often
ommitted)
• di =2
• tri =3
• tetra =4
• penta - =5
• Name: NO2
•
•
•
•
•
•
•
•
hexa - = 6
hepta - = 7
octa =8
nona - = 9
Deca = 10
Name: N2O5
SF6
CO
Binary Acids
• Formed from a hydrogen bonded to many
nonmetals. e.g. HCl, HBr, HI, H2S, etc.
• Acid name (in an aqueous solution)
– Prefix – hydro
– Suffix - change ide to ic
• HCl – hydrogen chloride ==> hydrochloric acid
• H2S – hydrogen sulfide ==> hydrosulfuric acid
• HI – hydrogen iodide ==> hydroiodic acid
Acid Base Reactions
• Acids react with a base such as NaOH to
produce water and a salt (an ionic
compound)
• Neutralization reaction
• HCl reacts with NaOH to yield water and
NaCl - table salt
23
Oxoacids
• Oxoacids contain hydrogen, oxygen and
another element.
• Named from the polyatomic ion
– eg. HNO3 becomes nitric acid
• Nitrate ==> nitric
– eg. HNO2 becomes nitrous acid
• Nitrite ==> nitrous
• HClO4 = ?
HClO3 = ?
Naming Inorganic Compounds
Copyright 2000 John Wiley and Sons, Inc.
Continued on next slide
24