Elements and Compounds
Chapter 3
Hein and Arena
Version 2.0
12th Edition
Eugene Passer
Chemistry Department
Bronx Community
1 College
© John Wiley and Sons, Inc
Chapter Outline
3.1 Elements
3.2 Distribution of Elements
3.6 Elements in Their Natural
States
3.7
3.3 Names of the Elements
Elements that Exist as
Diatomic Molecules
3.4 Symbols of the Elements
3.8 Compounds
3.5 Introduction to the
Periodic Table
3.9 Chemical Formulas
2
3.1
Elements
3
An element is a fundamental or
elementary substance that cannot be
broken down into simpler substances by
chemical means.
4
• All known substances on Earth and
probably the universe are formed by
combinations of more than 100
elements.
• Each element has a number.
– Beginning with hydrogen as 1, the
elements are numbered in order of
increasing complexity.
5
• Most substances can be decomposed
into two or more simpler substances.
– Water can be decomposed into hydrogen
and oxygen.
– Table salt can be decomposed into
sodium and chlorine.
• An element cannot be decomposed into
a simpler substance.
6
ATOM
• The smallest particle of an element that
can exist.
• The smallest unit of an element that
can enter into a chemical reaction.
7
3.2
Distribution of
Elements
8
• Elements are not distributed equally
by nature.
– Oxygen is the most abundant element in
the human body (65%).
– Oxygen is the most abundant element in
the crust of the earth (49.2%).
• In the universe, the most abundant
element is hydrogen (91%) and the
second most abundant element is
helium (8.75%).
9
Distribution of the
common elements
in nature.
10
3.2
3.3
Names
of the Elements
11
Sources of Element Names
GreekColor
• Iodine: from the Greek iodes meaning
violet.
Latin• Fluorine: from the Latin fluere meaning
Property to flow. The fluorine containing ore
fluorospar is low melting.
German- • Bismuth: from the German
Color
weisse mass which means white mass.
Location • Germanium: discovered in 1866 by a
German chemist.
Famous- • Einsteinium: named for Albert Einstein.
12
Scientists
3.4
Symbols
of the Elements
13
• A symbol stands for
– the element itself
– one atom of the element
– a particular quantity of the element
14
Rules governing symbols of the elements
are:
1. Symbols have either one or
two letters.
2. If one letter is used it is
capitalized.
H carbon
C
hydrogen
3. If two letters are used, only Ba
Ne barium
neon
the first is capitalized.
15
These symbols have carried over from the earlier names of the
elements
(usually
Latin).
A number
Mostofsymbols
symbolsstart
appear
withtothe
have
same
noletter
connection
as the element.
with the element.
16
17
Metals, Nonmetals
and Metalloids
18
Metals
19
• Metals are solid at room temperature.
– Mercury is an exception. At room temperature it
is a liquid.
• Metals are good conductors of heat and electricity.
Most elements
are metals
physical
properties
of metals
• Metals are malleable (they can be rolled
or
hammered into sheets).
• Metals have high luster (they are shiny).
20
• Metals are ductile (they can be drawn into wires).
• Most metals have a high melting point.
Most elements
are metals
• Metals have high densities
21
Examples of Metals
lead
gold
iron
22
Chemical Properties of Metals
• Metals have little tendency to combine with
each other to form compounds.
• Many metals readily combine with nonmetals
to form ionic compounds.
– They can combine with sulfur.
oxygen.
chlorine.
– In nature, minerals are formed by combinations
of the more reactive metals with other elements.
23
Chemical Properties of Metals
– A few of the less reactive metals such as copper,
silver and gold are found in the free state.
– Metals can mix with each other to form alloys.
 Brass is a mixture of copper and zinc.
 Bronze is a mixture of copper and tin.
 Steel is a mixture of carbon and iron.
24
Nonmetals
25
Physical Properties of Nonmetals
• Lack luster (they are dull)
• Have relatively low melting points
• Have low densities.
• Poor conductors of heat and electricity
• At room temperature, carbon, phosphorous,
sulfur, selenium, and iodine are solids.
26
Physical State at Room Temperature
phosphorous
carbon
Solid
selenium
sulfur
iodine
27
Physical State at Room Temperature
liquid
bromine
28
Physical State at Room Temperature
nitrogen,
oxygen
gas
fluorine,
chlorine
helium, neon, argon, krypton, xenon, radon
29
Metalloids
30
Metalloids have properties that
are intermediate between metals
and nonmetals
31
The Metalloids
1. boron
2. silicon
3. germanium
4. arsenic
5. antimony
6. tellurium
7. polonium
32
Nonmetals
arefound
foundtotothe
theleft
right
metalloids.
Metals are
ofofthethemetalloids
33
3.5
Introduction to the
Periodic Table
34
• The periodic table was designed by
Dimitri Mendelev in 1869.
• In the table each element’s symbol is
placed inside of a box.
• Above the symbol of the element is its
atomic number.
7
N
35
• The elements are arranged in order of
increasing atomic number.
• Elements with similar chemical
properties are organized in columns
called families or groups .
He
Ne
Ar
Kr
These elements are known
as the noble gases. They are
nonreactive.
Xe
Rn
36
3.6
Elements in Their
Natural States
37
Most substances around us are
mixtures or compounds.
THE NOBLE METALS
Some elements are
found in pure form.
• Gold
Au
• Silver
Ag
• Platinum Pt
38
Most substances around us are
mixtures or compounds.
THE NOBLE GASES
Some elements are
found in pure form.
•
•
•
•
•
•
Helium He
Neon
Ne
Argon Ar
Krypton Kr
Xenon Xe
Radon Rn
39
Most substances around us are
mixtures or compounds.
• Air is composed mainly of
nitrogen and oxygen gases.
• Nitrogen and oxygen are
composed of tiny two atom
molecules of N2 and O2.
40
3.7
Elements That Exist as
Diatomic Molecules
41
A diatomic molecule contains exactly two
atoms of the same or different elements.
42
43
Occurrence of Diatomic Molecules
Hydrogen
H
Hydrogen
H2
Nitrogen
N
Nitrogen
N2
Not found in
nature.
Found in
nature.
Not found in
nature.
Found in
nature.
44
• Hydrogen gas is found in volcanoes
and it can be prepared in the
laboratory.
• In both cases it is diatomic hydrogen,
H2.
• Air is about 21% oxygen by volume.
• Oxygen can also be prepared in the
laboratory.
• In both cases it is diatomic oxygen, O2.
45
• Water has the formula H2O.
• It does not contain free hydrogen, H2
or free oxygen, O2.
• The H2 part of H2O means that 2 atoms
of hydrogen are combined with one
atom of oxygen in the water molecule.
H2
O2
46
H2O
3.8
Compounds
47
A compound is a distinct substance that
contains two or more elements combined
in a definite proportion by weight.
48
• Compounds can be decomposed
chemically into simpler substances–
that is, into simpler compounds or
elements.
• Elements cannot be decomposed into
simpler substances.
• Atoms of the elements that constitute a
compound are always present in simple
whole number ratios. They are never
present as fractional parts.
49
There are two types of compounds:
molecular and ionic.
50
Molecules
51
A molecule is the smallest uncharged
individual unit of a compound formed by
the union of two or more atoms.
52
• A water molecule consists of two
hydrogen atoms and one oxygen atom.
• If it is subdivided the water molecule
will be destroyed and hydrogen and
oxygen will be formed.
53
3.5
Ionic Compounds
54
An ion is a positively or negatively
charged atom or group of atoms.
55
A cation is a positively charged ion.
56
3.5
An anion is a negatively charged ion.
57
3.5
Ionic compounds are held together by
attractive forces between positively and
negatively charged ions.
58
Sodium Chloride
• Sodium chloride is a colorless crystalline
ionic substance.
• It is 39.3% sodium and 60.7% chlorine
by mass.
• The solid does not conduct electricity.
• Passing an electric current through the
molten salt produces solid sodium and
gaseous chlorine.
59
Sodium Chloride
The ultimate particles of sodium chloride
are positively charged sodium ions and
negatively charged chloride ions.
60
3.5
Sodium Chloride
The crystalline structure of sodium chloride is
held together by the attractive forces between
the positive sodium ions and the negative
chloride ions.
61
Ionic Compound Formulas
62
The actualchloride
Sodium
chemical and
formulas
otherof ionic
compounds express
consist of
thelarge
smallest
aggregates
whole
of cationsratio
number
and anions.
that exists between the
cations and the anions.
63
• The formula NaCl does not mean that
a molecule of NaCl exists.
• The formula NaCl means that the
ratio of sodium to chlorine in a
sodium chloride crystal is one to one.
64
The ratio of Na+ to Cl- is 1:1
65
Compounds can be classified as molecular or
ionic. Ionic compounds are held together by
attractive forces between their positive and
negative charges. Molecular compounds are
held together by covalent bonds.
66
3.3
3.9
Chemical Formulas
67
chemical
formulas
Serve as abbreviations of the
names of compounds.
CaCl2
calcium
chloride
68
chemical
formulas
Tell which elements the
compound is composed of
and how many atoms of each
element are present in a
formula unit.
CaCl2
calcium
chlorine
69
chemical
formulas
Show the symbols of the atoms
of the elements present in a
compound.
CaCl2
Ca calcium
Cl chlorine
70
chemical
formulas
Show the ratio of the atoms of
the elements present in a
compound.
CaCl2
2 Cl
1 Ca
71
Rules for Writing
Chemical Formulas
72
When a formula contains one atom of an
element, the symbol of that element
represents the one atom. The number one
(1) is not used as a subscript.
73
NaCl
indicates
the element sodium
(one atom)
indicates
the element chlorine
(one atom)
74
When the formula contains more than
one atom of an element, the number of
atoms is indicated by a subscript written
to the right of the symbol of that atom.
75
H3PO4
indicates
the element
hydrogen (H)
indicates
the element
oxygen (O)
indicates
4 O atoms
indicates
3 H atoms
indicates
the element
phosphorous (P)
76
When the formula contains more than
one of a group of atoms that occurs as a
unit, parentheses are placed around the
group, and the number of units of the
group is indicated by a subscript placed
to the right of the parentheses.
77
indicates
the element
barium
indicates two
3phosphate (PO 4 )
groups
Ba3(PO4)2
indicates three
Ba atoms
indicates the phosphate group
composed of one phosphorous
atom and four oxygen atoms
78
Formulas written as H2O, H2SO4,
Ca(NO3)2 and C12H22O11 show only the
number and kind of each atom contained
in the compound; they do not show the
arrangements of the atoms in the
compound or how they are chemically
bonded to each other.
79
H2O
80
81