Download Chapter 3 Atoms and Elements

Chapter 3
Atoms and Elements
Matter
3.1
Classification of Matter
Matter is the “stuff” that
makes up all things.
Copyright © 2009 by Pearson Education, Inc.
Copyright © 2009 by Pearson Education, Inc.
1
Pure Substances
2
Elements
Elements are
• pure substances that
contains atoms of only
one type.
A pure substance is classified as
• matter with a specific composition.
• an element when composed of one type of atom.
• a compound when composed of two or more
Copper, Cu
Lead, Pb
Aluminum, Al
elements combined in a definite ratio.
Copyright © 2009 by Pearson Education, Inc.
3
Compounds
4
Elements in a Compound
Compounds
“Table salt” is a compound that contains the elements
sodium and chlorine.
• contain two or more elements
in a definite ratio.
Salt (NaCl)
Table sugar (C12H22O11)
Water (H2O)
Copyright © 2009 by Pearson Education, Inc.
5
6
Mixtures
Physical Separation of a Mixture
A mixture is a type of matter that consists of
• two or more substances that are physically mixed, not
chemically combined.
• two or more substances in different proportions.
• substances that can be separated by physical
methods.
Example:
Pasta and water are separated with a strainer.
Copyright © 2009 by Pearson Education, Inc.
7
Homogeneous Mixtures
8
Heterogeneous Mixtures
In a homogeneous mixture,
In a heterogeneous mixture,
• the composition of
substances is not uniform.
• the composition varies from
one part of the mixture to
another.
• the different parts of the
mixture are visible.
• the composition is uniform
throughout.
• the different parts of the
mixture are not visible.
Copyright © 2009 by Pearson Education, Inc.
Copyright © 2009 by Pearson Education, Inc.
9
Classification of Matter
10
Learning Check
Identify each of the following as a pure substance or a
mixture.
A. pasta and tomato sauce
B. aluminum foil
C. helium
D. air
11
12
Solution
Learning Check
Identify each of the following as a pure substance or a
mixture.
Identify each of the following as a homogeneous or
heterogeneous mixture:
A. pasta and tomato sauce
mixture
A. hot fudge sundae
B. aluminum foil
pure substance
B. air
C. helium
pure substance
C. sugar water
D. air
mixture
D. peach pie
13
14
Chapter 3
Solution
Identify each of the following as a homogeneous or
heterogeneous mixture:
A. hot fudge sundae
heterogeneous mixture
B. air
homogeneous mixture
C. sugar water
homogeneous mixture
D. peach pie
heterogeneous mixture
Atoms and Elements
3.2
Elements and Symbols
Copyright © 2009 by Pearson Education, Inc.
15
Elements
16
Sources of Some Element Names
Elements are
• pure substances that cannot be separated into
•
Some elements are
named for planets,
mythological
figures,
minerals, colors,
scientists, and
places.
simpler substances by ordinary laboratory
processes.
the building blocks of matter.
gold
carbon
aluminum
17
18
Symbols of Elements
Symbols from Latin Names
A symbol
• represents the name of an element.
• consists of 1 or 2 letters.
• starts with a capital letter.
1-Letter Symbols
C carbon
N nitrogen
F
fluorine
O oxygen
Mg
Several symbols are derived from Latin names as shown
below.
2-Letter Symbols
Co
cobalt
Ca
calcium
Al
aluminum
magnesium
Cu, copper (cuprum)
Au, gold (aurum)
Fe, iron (ferrum)
Ag, silver (argentum)
Copyright © 2009 by Pearson Education, Inc.
19
Physical Properties of Elements
Physical Properties of Elements
The physical properties of an element
• are observed or measured without changing its
identity.
• include the following:
Shape
Color
Odor and taste
20
Some physical properties of
copper are:
Color
Luster
Melting point
Boiling point
Conduction
of electricity
Conduction
of heat
Density
Melting point
Boiling point
Red-orange
Very shiny
1083 °C
2567 °C
Excellent
Excellent
21
Learning Check
Copyright © 2009 by Pearson Education, Inc.
22
Solution
Select the correct symbol for each.
A. Calcium
2) Ca
Select the correct symbol for each.
A. Calcium
1) C
2) Ca
3) CA
B. Sulfur
1) S
2) Sl
3) Su
B. Sulfur
1) S
C. Iron
1) Ir
2) FE
3) Fe
C. Iron
3) Fe
23
24
Learning Check
Solution
Select the correct name for each symbol.
A. N
1) neon
2) nitrogen
3) nickel
Select the correct name for each:
A. N
2) nitrogen
B. P
1) potassium
2) phlogiston
3) phosphorus
B. P
3) phosphorus
C. Ag
1) silver
2) agean
3) gold
C. Ag
1) silver
25
Chapter 3 Atoms and Elements
26
Groups and Periods
3.3
The Periodic Table
On the periodic table,
• elements are arranged according to similar
properties.
• groups contain elements with similar properties in
vertical columns.
• periods are horizontal rows of elements.
Copyright © 2009 by Pearson Education, Inc.
27
Groups and Periods
28
Periodic Table
Copyright © 2009 by Pearson Education, Inc.
29
30
Names of Some Representative
Elements
Group Numbers
Group Numbers
• use the letter A for the representative elements (1A to
8A) and the letter B for the transition elements.
• also use numbers 1-18 to the columns from left to right.
31
Alkali Metals
32
Halogens
Group 1A (1), the alkali metals, includes lithium,
sodium, and potassium.
Group 7A (17),
the halogens,
includes chlorine,
bromine, and
iodine.
Copyright © 2009 by Pearson Education, Inc.
Copyright © 2009 by Pearson Education, Inc.
33
Learning Check
Solution
Identify the element described by the following:
A. Group 7A (17), Period 4
1) Br
2) Cl
34
A. Group 7A (17), Period 4
1) Br
B. Group 2A (2), Period 3
3) Mn
3) magnesium
B. Group 2A (2), Period 3
1) beryllium
2) boron
3) magnesium
C. Group 5A (15), Period 2
1) phosphorus 2) arsenic
3) nitrogen
C. Group 5A (15), Period 2
3) nitrogen
35
36
Metals, Nonmetals, and Metalloids on
the Periodic Table
Metals, Nonmetals, and Metalloids
The heavy zigzag line separates metals and
nonmetals.
• Metals are located to the left.
• Nonmetals are located to the right.
• Metalloids are located along the heavy zigzag
line between the metals and nonmetals.
37
Properties of Metals, Nonmetals, and
Metalloids
38
Comparing a Metal, Metalloid, and
Nonmetal
Metals
• are shiny and ductile.
• are good conductors of heat and electricity.
Nonmetals
• are dull, brittle, and poor conductors.
• are good insulators.
Metalloids
• are better conductors than nonmetals, but not
as good as metals.
• are used as semiconductors and insulators.
39
Learning Check
40
Solution
Identify each of the following elements as
1) metal, 2) nonmetal, or 3) metalloid.
Identify each of the following elements as
1) metal, 2) nonmetal, or 3) metalloid.
A. sodium
B. chlorine
C. silicon
D. iron
E. carbon
A. sodium
B. chlorine
C. silicon
D. iron
E. carbon
____
____
____
____
____
41
1 metal
2 nonmetal
3 metalloid
1 metal
2 nonmetal
42
Learning Check
Solution
Match the elements to the description.
Match the elements to the description.
A. Metals in Group 4A (14)
1) Sn, Pb
2) C, Si
3) C, Si, Ge, Sn
A. Metals in Group 4A (14)
1) Sn, Pb
B. Nonmetals in Group 5A (15)
1) As, Sb, Bi
2) N, P
3) N, P, As, Sb
B. Nonmetals in Group 5A (15)
2) N, P
C. Metalloids in Group 4A (14)
1) C, Si, Ge,
2) Si, Ge
3) Si, Ge, Sn, Pb
C. Metalloids in Group 4A (14)
2) Si, Ge
43
Chapter 3 Atoms and Elements
44
Dalton’s Atomic Theory
3.4
The Atom
In Dalton’s atomic theory, atoms
• are tiny particles of matter.
• of an element are similar and
different from other elements.
• of two or more different elements
combine to form compounds.
• are rearranged to form new
combinations in a chemical
reaction.
Copyright © 2009 by Pearson Education, Inc.
45
Subatomic Particles
Rutherford’s Gold Foil Experiment
Atoms contain subatomic particles.
•
•
•
•
46
In Rutherford’s gold foil experiment, positively
charged particles
•
were aimed at atoms of gold.
•
mostly went straight through the atoms.
•
were deflected only occasionally.
Protons have a positive (+) charge.
Electrons have a negative (-) charge.
Neutrons are neutral.
Like charges repel and unlike charges
attract.
Conclusion:
There must be a small, dense, positively
charged nucleus in the atom that deflects
positive particles that come close.
47
48
Rutherford’s Gold Foil Experiment
Structure of the Atom
An atom consists
• of a nucleus that
contains protons
and neutrons.
• of electrons in a
large, empty
space around the
nucleus.
Copyright © 2009 by Pearson Education, Inc.
Copyright © 2009 by Pearson Education, Inc.
49
Atomic Mass Scale
50
Particles in the Atom
On the atomic mass scale,
• 1 atomic mass unit (amu) has a mass equal to 1/12 of
the mass of the carbon-12 atom.
• a proton has a mass of about 1 (1.007) amu.
• a neutron has a mass of about 1 (1.008) amu.
• an electron has a very small mass, 0.000 549 amu.
51
Learning Check
52
Solution
Identify each statement as describing a
1) proton, 2) neutron, or 3) electron.
Identify each statement as describing a
1) proton, 2) neutron, or 3) electron.
A. found outside the nucleus
B. has a positive charge
C. is neutral
D. found in the nucleus
A. 3
B. 1
C. 2
D. 1, 2
53
found outside the nucleus
has a positive charge
is neutral
found in the nucleus
54
Chapter 3
Atoms and Elements
Atomic Number
3.5
Atomic Number and Mass Number
The atomic number
• is specific for each element.
• is the same for all atoms of an element.
• is equal to the number of protons in an atom.
• appears above the symbol of an element.
Atomic Number
Symbol
11
Na
Copyright © 2009 by Pearson Education, Inc.
55
Atomic Number and Protons
56
Learning Check
Examples of atomic number and number of protons:
• Hydrogen has atomic number 1; every H atom has
one proton.
• Carbon has atomic number 6; every C atom has six
protons.
• Copper has atomic number 29; every Cu atom has
29 protons.
• Gold has atomic number 79; every Au atom has 79
State the number of protons in each.
A. A nitrogen atom
1) 5 protons
2) 7 protons
3) 14 protons
B. A sulfur atom
1) 32 protons
2) 16 protons
3) 6 protons
C. A barium atom
1) 137 protons
2) 81 protons
3) 56 protons
protons.
57
Solution
58
Electrons in An Atom
State the number of protons in each.
A. A nitrogen atom
2) atomic number 7; 7 protons
An atom
• of an element is electrically neutral; the net charge
of an atom is zero.
• has an equal number of protons and electrons.
number of protons = number of electrons
B. A sulfur atom
2) atomic number 16; 16 protons
Aluminum has 13 protons and 13 electrons. The net
(overall) charge is zero.
13 protons (13+) + 13 electrons (13 -) = 0
C. A barium atom
3) atomic number 56; 56 protons
59
60
Mass Number
Atomic Models
The mass number
• represents the number of particles in the nucleus.
• is equal to the number of protons + the number
of neutrons.
61
Learning Check
62
Solution
An atom of zinc has a mass number of 65.
A. How many protons are in this zinc atom?
1) 30
(atomic number 30)
An atom of zinc has a mass number of 65.
A. How many protons are in this zinc atom?
1) 30
2) 35
3) 65
B. How many neutrons are in the zinc atom?
2) 35
(65 – 30 = 35)
B. How many neutrons are in the zinc atom?
1) 30
2) 35
3) 65
C. What is the mass number of a zinc atom that has 37
neutrons?
3) 67
(30 + 37 = 67)
C. What is the mass number of a zinc atom that has
37 neutrons?
1) 37
2) 65
3) 67
63
Learning Check
64
Solution
An atom has 14 protons and 20 neutrons.
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
3) 34
A. It has atomic number
1) 14
2) 16
3) 34
B. It has a mass number of
3) 34
(14 + 20 = 34)
2) Ca
3) Se
C. The element is
1) Si
(Atomic number 14)
1) 14
2) 16
B. Its mass number is
1) 14
C. The element is
1) Si
65
66
Chapter 3
Atoms and Elements
Isotopes
3.6
Isotopes and Atomic Mass
Isotopes
• are atoms of the same element that have different
mass numbers.
• have the same number of protons, but different
numbers of neutrons.
24Mg
25Mg
26Mg
12
12
12
Copyright © 2009 by Pearson Education, Inc.
67
Atomic Symbol
68
Information from Atomic Symbols
The atomic symbol for a specific atom of an element
An atomic symbol
gives the
• represents a particular atom of an element.
• gives the mass number in the upper left corner and
• number of protons (p+),
• number of neutrons (n),
• and number of electrons (e-).
the atomic number in the lower left corner.
Example: An atom of sodium with atomic number 11
and a mass number 23 has the following atomic
symbol:
mass number
23
Na
atomic number
11
69
Information from Atomic Symbols
Learning Check
Examples of number of subatomic particles for atoms
Naturally occurring carbon consists of three isotopes:
12C, 13C, and 14C. State the number of protons,
neutrons, and electrons in each of the following:
Atomic symbol
16
8
31
O
8 p+
8n
8 e-
P
15
15 p+
16 n
15 e-
70
65
Zn
12C
30
6
30 p+
35 n
30 e-
71
13C
6
14C
6
protons
______
______
______
neutrons
______
______
______
electrons ______
______
______
72
Solution
Learning Check
12C
6
13C
14C
6
6
protons
6 p+
6 p+
neutrons
6n
7n
8n
electrons 6 e-
6 e-
6 e-
Write the atomic symbols for atoms with the
following subatomic particles:
6 p+
A. 8 p+, 8 n, 8 e-
___________
B. 17p+, 20n, 17e-
___________
C. 47p+, 60 n, 47 e-
___________
73
Solution
Learning Check
A. 8 p+, 8 n, 8 e-
1. Which of the pairs are isotopes of the same element?
2. In which of the pairs do both atoms have 8 neutrons?
16O
8
B.
17p+,
74
20 n,
17e-
37Cl
A.
17
C. 47p+, 60 n, 47 e-
15X
8
107Ag
B.
47
C.
12X
15X
7
14X
6
6
15X
16X
7
8
75
Solution
B.
12X
6
76
Isotopes of Magnesium
14X
6
The atomic symbols in “B.” represent isotopes of
carbon with 6 protons each, but one has 6 neutrons
and the other has 8.
C.
15X
7
16X
8
These isotopes of nitrogen and oxygen have 8
neutrons.
77
78
Isotopes of Magnesium
Isotopes of Sulfur
A sample of naturally
occurring sulfur contains
several isotopes with the
following abundances
Isotope % abundance
32S
95.02
33S
0.75
34S
4.21
36S
0.02
32S, 33S, 34S, 36S
16
16
16
16
Copyright © 2009 by Pearson Education, Inc.
79
Isotopes of Some Elements and Their
Atomic Mass
Atomic Mass
Most elements have two or more isotopes that
contribute to the atomic mass of that element.
The atomic mass of an element
• is listed below the symbol of each element
on the periodic table.
• gives the mass of an “average” atom of
80
Na
22.99
each element compared to 12C.
• is not the same as the mass number.
81
Atomic Mass for Cl
82
Learning Check
The atomic mass of chlorine is
Using the periodic table, specify the atomic mass of
each element.
• due to all the Cl isotopes.
• not a whole number.
• the average of two isotopes:
35Cl
and 37Cl.
83
A. calcium
__________
B. aluminum
__________
C. lead
__________
D. barium
__________
E. iron
__________
84
Solution
Calculating Atomic Mass
Using the periodic table, specify the atomic mass of
each element:
A. calcium
40.08 amu
B. aluminum
26.98 amu
C. lead
207.2 amu
D. barium
137.3 amu
E. iron
55.85 amu
The calculation for atomic mass requires the
• percent(%) abundance of each isotope.
• atomic mass of each isotope of that element.
• sum of the weighted averages.
mass of isotope(1)x (%) + mass of isotope(2) x (%) +
100
100
85
Calculating Atomic Mass for Cl
35Cl
86
Calculating Atomic Mass Mg
Isotope Mass
has atomic mass 34.97 amu (75.76%) and 37C
Abundance
has atomic mass 36.97 amu (24.24%).
24Mg
= 23.99 amu x 78.70/100
= 18.88 amu
• Use atomic mass and percent of each isotope to
calculate the contribution of each isotope to the
weighted average.
=
26.49 amu
34.97 x 75.76
100
=
8.961 amu
36.97 x 24.24
100
25Mg
= 24.99 amu x 10.13/100
= 2.531 amu
26Mg
= 25.98 amu x 11.17/100 =
• Sum is atomic mass of Cl
Atomic mass (average mass) Mg
2.902 amu
= 24.31 amu
35.45 amu
87
88
Learning Check
Atomic Mass of Magnesium
The atomic mass of Mg
• is due to all the Mg
isotopes.
• is a weighted average.
• is not a whole number.
Gallium is an element found in lasers used in compact
disc players. In a sample of gallium, there is 60.10%
of 69Ga (atomic mass 68.926) atoms and 39.90% of
71Ga (atomic mass 70.925) atoms.
What is the atomic mass of gallium?
89
90
Chapter 3 Atoms and Elements
Solution
69Ga
68.926 amu x
60.10
100
3.7
Electron Energy Levels
= 41.42 amu (from 69Ga)
71Ga
70.925 amu x 39.90 = 28.30 amu (from 71Ga)
100
31
Atomic mass Ga
= 69.72 amu
Ga
69.72
Copyright © 2009 by Pearson Education, Inc.
91
Energy Levels
92
Energy Levels
Energy levels
• are assigned numbers n =
1, 2, 3, 4, and so on.
• increase in energy as the
value of n increases.
• are like the rungs of a
ladder with the lower
energy levels nearer the
nucleus.
Energy levels have a maximum number of electrons
equal to 2n2.
Energy level
n=1
n=2
n=3
Maximum number of electrons
2(1)2 = 2(1) = 2
2(2)2 = 2(4) = 8
2(3)2 = 2(9) = 18
93
Orbitals
94
Orbitals
An orbital
• is a three-dimensional space around a nucleus,
where an electron is most likely to be found.
An s orbital
•has a spherical shape around the nucleus.
•is found in each energy level.
• has a shape that represents electron density (not
a path the electron follows).
A p orbital
• has a two-lobed shape.
• can hold up to 2 electrons.
• is one of three p orbitals in each energy level from n = 2.
95
96
Electron Level Arrangement
Orbitals
In the electron level arrangement for the first 18
elements
• electrons are placed in energy levels (1, 2, 3, etc.),
beginning with the lowest energy level
• there is a maximum number in each energy level.
Energy level
Number of electrons
1
2 (up to He)
2
8 (up to Ne)
3
8 (up to Ar)
4
2 (up to Ca)
97
Learning Check
98
Solution
Write the electron level arrangement for each:
Write the electron level arrangement for each:
1. N
1. N
2, 5
2. Cl
2. Cl
2, 8, 7
3. K
3. K
2, 8, 8, 1
99
Learning Check
100
Solution
Identify the element with each electron level
arrangement:
Identify the element with each electron level
arrangement:
1. 2, 2
1. Be
2, 2
2. 2, 8, 3
2. Al
2, 8, 3
3. 2, 7
3. F
2, 7
101
102
Chapter 3 Atoms and Elements
3.8
Periodic Trends
Copyright © 2009 by Pearson Education, Inc.
104
Valence Electrons
Groups and Valence Electrons
The valence electrons
• determine the chemical properties of the elements.
• are the electrons in the highest energy level.
• are related to the group number of the element.
All the elements in a group have the same number of
valence electrons.
Example: Elements in group 2A (2) have two (2)
valence electrons.
Be
2, 2
Mg
2, 8, 2
Ca
2, 8, 8, 2
Sr
2, 8, 18, 8, 2
Example: Phosphorus has 5 valence electrons.
5 valence electrons
P in Group 5A(15)
2, 8, 5
105
Periodic Table and Valence Electrons
Representative Elements Group Numbers
1
2
3
4
5
6
7
H
1
Li
2,1
Be
2,2
B
2,3
C
2,4
N
2,5
Na
Mg Al
Si
2,8,1 2,8,2 2,8,3 2,8,4
P
2,8,5
O
2,6
S
2,8,6
F
2,7
106
Learning Check
State the number of valence electrons for each.
A. O
8
He
2
1) 4
2) 6
3) 8
2) 3
3) 1
2) 5
3) 7
B. Al
Ne
2,8
1) 13
Cl
Ar
2,8,7 2,8,8
107
C. Cl
1) 2
108
Solution
Learning Check
State the number of valence electrons for each.
A. O
State the number of valence electrons for each.
A. calcium
1) 1
2) 2
3) 3
2) 6
B. Al
2) 3
C. Cl
3) 7
B. group 6A (16)
1) 2
2) 4
3) 6
C. tin
1) 2
2) 4
3) 14
109
Solution
110
Learning Check
State the number of valence electrons for each.
A. calcium
2) 2
For the element with the following electron arrangement:
1) State the number of valence electrons.
2) Identify the element.
B. group 6A (16)
3) 6
A. 2, 8, 5
B. 2, 8, 8, 2
C. 2, 7
C. tin
2) 4
111
Solution
112
Electron-Dot Symbols
An electron-dot symbol
• shows the valence electrons
around the symbol of the
element.
• for Mg has 2 valence electrons
as single dots on the sides of
the symbol Mg.
.
.
·Mg · or Mg · or ·Mg or ·Mg
·
For the element with the following electron arrangement
1) State the number of valence electrons
2) Identify the element.
A. 2, 8, 5
1) 5
2) phosphorus
B. 2, 8, 8, 2
1) 2
2) calcium
C. 2, 7
1) 7
2) fluorine
113
114
Writing Electron-Dot Symbols
Groups and Electron-Dot Symbols
In a group, all the electron-dot symbols have the
same number of valence electrons (dots).
Electron-dot symbols for
• groups 1A (1) to 4A (14) use single dots.
·
·
Na ·
· Mg ·
· Al ·
·C·
·
Example: Atoms of elements in Group 2A (2) each
have 2 valence electrons.
· Be ·
· Mg ·
· Ca ·
· Sr ·
· Ba ·
• groups 5A (15) to 7A (17) use pairs and single
dots.
··
·P·
·
··
: O·
·
115
Learning Check
Solution
A.
.
X is the electron-dot symbol for
B.
..
.X.
.
1) Na
2) K
A.
3) Al
2) N
.
X is the electron-dot symbol for
1) Na
B.
is the electron-dot symbol of
1) B
116
3) P
2) K
..
.X .
. is the electron-dot symbol of
2) N
3) P
117
Atomic Size
118
Atomic Radius Within A Group
Atomic size is described
Atomic radius increases
going down each group
of representative
elements.
using the atomic radius;
the distance from the
nucleus to the valence
electrons.
119
120
Atomic Radius Across a Period
Learning Check
Going across a period from left to right,
• an increase in the number of protons increases
attraction for valence electrons.
• atomic radius decreases.
Select the element in each pair with the larger atomic
radius.
A.
B.
C.
Li or K
K or Br
P or Cl
Copyright © 2009 by Pearson Education, Inc.
121
Solution
122
Ionization Energy
Select the element in each pair with the larger atomic
radius.
Ionization energy is the energy it takes to remove a
valence electron.
Na(g) + Energy (ionization) -> Na+(g) + e-
A. K
B. K
C. P
123
Ionization Energy In a Group
124
Ionization Energy
Going up a group of
representative elements,
• the distance decreases
between nucleus and
valence electrons.
• Metals have
•
• the ionization energy
increases.
lower
ionization
energies.
Nonmetals
have higher
ionization
energies.
Copyright © 2009 by Pearson Education, Inc.
125
126
Learning Check
Solution
Select the element in each pair with the higher ionization
energy.
Select the element in each pair with the higher ionization
energy.
A.
B.
C.
A.
B.
C.
Li or K
K or Br
P or Cl
127
Li
Br
Cl
128