Chapter 3 lecture presentation

General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc.
1
Chapter 3 Atoms and Elements
3.1
Elements and Symbols

2
Elements are
pure substances that cannot be separated into simpler substances by ordinary laboratory processes
the building blocks of matter
gold carbon aluminum
Elements

3
Sources of Some Element Names
Some elements are
named for planets,
mythological figures,
minerals, colors,
scientists, and places.

4
A symbol
represents the name of an element
consists of 1 or 2 letters
starts with a capital letter
Examples:
1-Letter Symbols 2-Letter Symbols
C carbon Co cobalt
N nitrogen Ca calcium
F fluorine Al aluminum
O oxygen Mg magnesium
Symbols of Elements

5
Some symbols are derived from Latin names, as shown
below.
Cu, copper (cuprum) Au, gold (aurum)
Fe, iron (ferrum) Ag, silver (argentum)
Symbols from Latin Names

6
Physical Properties of Elements
The physical properties of an element
are observed or measured without changing its identity
include the following:
shape
color
odor
taste
density
melting point
boiling point

7
Physical Properties of Elements
Some physical properties of copper are:
Color Red-orange
Luster Very shiny
Melting point 1083 °C
Boiling point 2567 °C
Conduction
of electricity Excellent
Conduction
of heat Excellent

8
Select the correct symbol for each of the following:
A. Calcium
1) C 2) Ca 3) CA
B. Sulfur
1) S 2) Sl 3) Su
C. Iron
1) Ir 2) FE 3) Fe
Learning Check

9
Select the correct symbol for each of the following:
A. Calcium
2) Ca
B. Sulfur
1) S
C. Iron
3) Fe
Solution

10
Select the correct name for each symbol.
A. N
1) neon 2) nitrogen 3) nickel
B. P
1) potassium 2) phlogiston 3) phosphorus
C. Ag
1) silver 2) agean 3) gold
Learning Check

11
Select the correct name for each symbol.
A. N
2) nitrogen
B. P
3) phosphorus
C. Ag
1) silver
Solution

12
3.2 The Periodic Table

13
Groups and Periods
On the periodic table
Groups contain elements with similar properties and are arranged in vertical columns.
Periods are the horizontal rows of elements.

14
Groups and Periods (continued)

15
Periodic Table

16
Group Numbers
Group Numbers
Use numbers 1–18 to identify the columns from left to right.
Use the letter A for the representative elements (1A to 8A) and the letter B for the transition elements.

17
Representative Elements
Several groups of representative elements are known by common names.

18
Alkali Metals
Group 1A(1), the alkali metals, includes lithium, sodium, and potassium.

19
Halogens
Group 7A(17), the halogens, includes chlorine, bromine, and iodine.

20
Identify the element described by the following:
A. Group 7A(17), Period 4
1) Br 2) Cl 3) Mn
B. Group 2A(2), Period 3
1) beryllium 2) magnesium 3) boron
C. Group 5A(15), Period 2
1) phosphorus 2) arsenic 3) nitrogen
Learning Check

21
A. Group 7A (17), Period 4
1) Br
B. Group 2A (2), Period 3
2) magnesium
C. Group 5A(15), Period 2
3) nitrogen
Solution

22
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.

23
Metals
are shiny and ductile
are good conductors of heat and electricity
Nonmetals
are dull, brittle, and poor conductors of heat and electricity
are good insulators
Metalloids
are better conductors than nonmetals, but not as good as metals
are used as semiconductors and insulators
Properties of Metals, Nonmetals, and Metalloids

24
Comparing a Metal, Metalloid, and Nonmetal

25
Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid.
A. sodium ____
B. chlorine ____
C. silicon ____
D. iron ____
E. carbon ____
Learning Check

26
Identify each of the following elements as 1) metal, 2) nonmetal, or 3) metalloid.
A. sodium 1 metal
B. chlorine 2 nonmetal
C. silicon 3 metalloid
D. iron 1 metal
E. carbon 2 nonmetal
Solution

27
Match the elements to the description.
A. Metals in Group 4A(14)
1) Sn, Pb 2) C, Si 3) C, Si, Ge, Sn
B. Nonmetals in Group 5A(15)
1) As, Sb, Bi 2) N, P 3) N, P, As, Sb
C. Metalloids in Group 4A(14)
1) C, Si, Ge, 2) Si, Ge 3) Si, Ge, Sn, Pb
Learning Check

28
Match the elements to the description.
A. Metals in Group 4A (14)
1) Sn, Pb
B. Nonmetals in Group 5A(15)
2) N, P
C. Metalloids in Group 4A(14)
2) Si, Ge
Solution

29
3.3 The Atom

30
Dalton’s Atomic Theory
Atoms
are tiny particles of matter
of an element are similar to each other but are different from atoms of other elements
of two or more different elements combine to form compounds
are rearranged to form new combinations in a chemical reaction

31
Subatomic Particles
Atoms contain subatomic particles.
Protons have a positive (+) charge.
Electrons have a negative (–) charge.
Like charges repel, and unlike
charges attract.
Neutrons are neutral.

32
Rutherford’s Gold-Foil Experiment
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
Conclusion:
There must be a small, dense, positively charged
nucleus in the atom that deflects positive particles
that come close.

33
Rutherford’s Gold-Foil Experiment (continued)

34
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

35
Atomic Mass Scale
On the atomic mass scale for subatomic particles:
1 atomic mass unit (amu) is defined as 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, 0.000549 amu.

36
Particles in the Atom

37
Learning Check
Identify each statement as describing a(n) 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

38
Solution
Identify each statement as describing a(n) 1) proton, 2) neutron, or 3) electron.
A. 3 found outside the nucleus
B. 1 has a positive charge
C. 2 is neutral
D. 1, 2 found in the nucleus

39
3.4 Atomic Number and Mass Number

40
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
11
Na
Atomic Number
Symbol

41
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 protons.
Atomic Number and Protons

42
State the number of protons in each.
A. A nitrogen atom
1) 5 protons 2) 7 protons 3) 14 protons
B. A sulfur atom
C. A barium atom
Learning Check

43
State the number of protons in each.
A. A nitrogen atom
2) atomic number 7; 7 protons
B. A sulfur atom
C. A barium atom,
Solution

44
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
of aluminum has 13 protons and 13 electrons; the net charge is zero
13 protons (13+) + 13 electrons (13–) = 0
Number of Electrons in an Atom

45
Mass Number
The mass number
represents the number of particles in the nucleus.
is equal to the
number of protons + number of neutrons

46
Atomic Models

47
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?
1) 30 2) 35 3) 65
C. What is the mass number of a zinc atom that has
37 neutrons?
1) 37 2) 65 3) 67
Learning Check

48
An atom of zinc has a mass number of 65.
A. How many protons are in this zinc atom?
1) 30 (atomic number 30)
B. How many neutrons are in the zinc atom?
2) 35 (65 – 30 = 35)
C. What is the mass number of a zinc atom that has 37 neutrons?
3) 67 (30 + 37 = 67)
Solution

49
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
1) 14 2) 20 3) 34
B. Its atomic number is
1) 14 2) 20 3) 34
C. The element is
1) Si 2) Ca 3) Se
Learning Check

50
3.5 Isotopes and Atomic Mass

51
Isotopes
are atoms of the same element that have different mass numbers
have the same number of protons but different numbers of neutrons
Isotopes

52
A nuclear symbol
represents a particular atom of an element
gives the mass number in the upper left corner and 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
atomic number
Nuclear Symbol
23
11
Na

53
For an atom, the nuclear symbol gives the number of
protons (p+)
neutrons (n)
electrons (e–)
8 p+ 15 p+ 30 p+
8 n 16 n 35 n
8 e– 15 e– 30 e–
Nuclear Symbols
16
8
O
31
15
P
65
30
Zn

54
Naturally occurring carbon consists of three isotopes, C-12, C-13, and C-14. State the number of protons, neutrons, and electrons in each of the following.
protons ______ ______ ______
neutrons ______ ______ ______
electrons ______ ______ ______
Learning Check
12
6
C
13
6
C
14
6
C

55
protons 6 p+ 6 p+ 6 p+
neutrons 6 n 7 n 8 n
electrons 6 e– 6 e– 6 e–
Solution
12
6
C
13
6
C
14
6
C

56
Write the nuclear symbols for atoms with the following subatomic particles:
A. 8p+, 8n, 8e– ___________
B. 17p+, 20n, 17e– ___________
C. 47p+, 60n, 47e– ___________
Learning Check

57
A. 8p+, 8n, 8e–
B. 17p+, 20n, 17e–
C. 47p+, 60n, 47e–
Solution
16
8
O
37
17
Cl
107
47
Ag

58
Learning Check
1. Which of the following pairs are isotopes of the same element?
2. In which of the following pairs do both atoms have
8 neutrons?
A.
B.
C.
12
6
X
15
7
X
12
6
Z
14
6
Z
15
7
Z
16
8
Z

59
Solution
1. B
Both nuclear symbols represent isotopes of carbon with six protons each, but one has 6 neutrons and the other has 8.
2. C
An atom of nitrogen (atomic number 7) and an atom of oxygen (atomic number 8) each have 8 neutrons.

60
Isotopes of Magnesium
In naturally occurring magnesium, there are 3 isotopes.

61
Isotopes of Sulfur
A sample of naturally
occurring sulfur contains
several isotopes with the
following abundances:
Isotope % Abundance
95.02
0.75
4.21
0.02
32
16
S
33
16
S
34
16
S
36
16
S
32 33 34 36
16 16 16 16
S S S S

62
Atomic Mass
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 each element compared to C-12
is not the same as the mass number
Na
22.99

63
Some Elements and Their Atomic Mass
Most elements have two or more isotopes that contribute to the atomic mass of that element.

64
Atomic Mass for Cl
The atomic mass of chlorine is
based on all naturally occurring Cl isotopes
not a whole number
the weighted average
of the Cl-35 and Cl-37
isotopes

65
Atomic Mass for Mg
The atomic mass of Mg is
based on all naturally occurring Mg isotopes
not a whole number
the weighted average
of the Mg-24, Mg-25, and
Mg-26 isotopes

66
Using the periodic table, give the atomic mass of
each element.
A. calcium __________
B. aluminum __________
C. lead __________
D. barium __________
E. iron __________
Learning Check

67
Using the periodic table, give 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
Solution

68
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
1) 14
B. Its atomic number is
3) 34 (14 + 20 = 34)
C. The element is
1) Si (atomic number 14)
Solution

69
3.6 Electron Energy Levels

70
Electromagnetic Radiation
Electromagnetic radiation
 is energy that travels as waves through space
 is described in terms of wavelength and
frequency
 moves at the speed of light in a vacuum
speed of light = 3.0 x 108 m/s

71
Electromagnetic Spectrum
The electromagnetic spectrum
arranges forms of energy from lowest to highest
arranges energy from longest to shortest wavelengths
shows visible light with wavelengths from 700–400 nm

72
Learning Check
1. Which of the following has the shortest wavelength?
A. microwaves B. blue light C. UV light
2. Which of the following has the lowest energy?
A. red light B. blue light C. green light

73
Solution
1. Which of the following has the shortest wavelength?
C. UV light
2. Which of the following has the lowest energy?
A. red light

74
Spectra
White light that passes
through a prism
is separated into all colors that together are called a continuous spectrum
gives the colors of a rainbow

75
Atomic Spectrum
An atomic spectrum consists of
lines of different colors formed when light from a heated element passes through a prism
photons emitted when electrons drop to lower energy levels

76
Example of Atomic Spectra

77
Electron Energy Levels
Electrons are arranged in
specific energy levels that
are labeled n = 1, n = 2, n = 3, and so on
increase in energy as n increases
have the electrons with the lowest energy in the first energy level (n = 1) closest to the nucleus

78
Energy Level Changes
An electron absorbs energy to “jump” to a higher energy level.
When an electron falls to a lower energy level, energy is emitted.
In the visible range, the emitted energy appears as a color.

79
In each of the following energy level changes, indicate
if energy is 1) absorbed, 2) emitted, or 3) not changed.
A. An electron moves from the first energy level (n = 1) to the third energy level (n = 3).
B. An electron falls from the third energy level to the second energy level.
C. An electron moves within the third energy level.
Learning Check

80
In each of the following energy level changes, indicate
if energy is 1) absorbed, 2) emitted, or 3) not changed.
A. An electron in an atom moves from the first energy level (n = 1) to the third energy level (n = 3).
1) absorbed
B. An electron falls from the third energy level to the second energy level.
2) emitted
C. An electron moves within the third energy level.
3) not changed
Solution

81
Sublevels
Sublevels
contain electrons with the same energy
are found within each energy level.
are designated by the letters s, p, d, and f
The number of sublevels is equal to the value of the principal quantum number (n).

82
Number of Sublevels

83
Energy of Sublevels
In any energy level
the s sublevel has the lowest energy
the s sublevel is followed by the p, d, and f sublevels (in order of increasing energy)
higher sublevels are possible, but only s, p, d, and f sublevels are needed to hold the electrons in the atoms known today

84
Orbitals
An orbital
is a three-dimensional space around a nucleus where an electron is most likely to be found
has a shape that represents electron density (not a path the electron follows)
can hold up to 2 electrons
contains two electrons that must spin in opposite

85
s Orbitals
An s orbital
has a spherical shape around the nucleus
increases in size around the nucleus as the energy level n value increases
is a single orbital found in each s sublevel

86
p Orbitals
A p orbital
has a two-lobed shape
is one of three p orbitals that make up each p sublevel
increases in size as the value of n increases

87
Sublevels and Orbitals
Each sublevel consists of a specific number of
orbitals.
An s sublevel contains one s orbital.
A p sublevel contains three p orbitals.
A d sublevel contains five d orbitals.
An f sublevel contains seven f orbitals.

88
Electrons in Each Sublevel

89
Learning Check
Indicate the number and type of orbitals in each of the
following:
A. 4s sublevel
B. 3d sublevel
C. n = 3

90
Solution
A. 4s sublevel
one 4s orbital
B. 3d sublevel
five 3d orbitals
C. n = 3
one 3s orbital, three 3p orbitals,
and five 3d orbitals

91
Learning Check
The number of
A. electrons that can occupy a p orbital is
1) 1 2) 2 3) 3
B. p orbitals in the 2p sublevel is
1) 1 2) 2 3) 3
C. d orbitals in the n = 4 energy level is
1) 1 2) 3 3) 5
D. electrons that can occupy the 4f sublevel is
1) 2 2) 6 3) 14

92
Solution
The number of
A. electrons that can occupy a p orbital is
2) 2
B. p orbitals in the 2p sublevel is
3) 3
C. d orbitals in the n = 4 energy level is
3) 5
D. electrons that can occupy the 4f sublevel is
3) 14

93
3.7 Electron Configurations

94
Energy levels are filled with electrons
in order of increasing energy
beginning with quantum number n = 1
beginning with s followed by p, d, and f
Order of Filling

95
Energy Diagram for Sublevels

96
An orbital diagram shows
orbitals as boxes in each sublevel
electrons in orbitals as vertical arrows
electrons in the same orbital with opposite spins (up and down vertical arrows)
Example:
Orbital diagram for Li
1s2 2s1 2p
filled half-filled empty
Orbital Diagrams

97
Order of Filling
Electrons in an atom
fill orbitals in sublevels of the same type with one electron each until all sublevels are half full
then pair up in the orbitals using opposite spins

98
Writing Orbital Diagrams
The orbital diagram
for carbon consists of
two electrons in the 1s orbital
two electrons in the 2s orbital
one electron each in two of the 2p orbitals

99
Write the orbital diagrams for
A. nitrogen
B. oxygen
C. magnesium
Learning Check

100
Write the orbital diagrams for
A. nitrogen
1s 2s 2p
B. oxygen
1s 2s 2p
C. magnesium
1s 2s 2p 3s
Solution

101
An electron configuration
lists the sublevels filling with electrons in order of increasing energy
uses superscripts to show the number of electrons in each sublevel
for neon is as follows:
number of electrons
sublevel 1s22s22p6
Electron Configuration

102
Period 1 Configurations
In Period 1, the first two electrons enter the 1s orbital

103
Abbreviated Configurations
An abbreviated configuration shows
the symbol of the noble gas in brackets that represents completed sublevels
the remaining electrons in order of their sublevels
Example: Chlorine has a configuration of
1s22s22p63s23p5
[Ne]
The abbreviated configuration for chlorine is
[Ne]3s23p5

104

105

106
A. The correct electron configuration for nitrogen is
1) 1s22p5 2) 1s22s22p6 3) 1s22s22p3
B. The correct electron configuration for oxygen is
1) 1s22p6 2) 1s22s22p4 3) 1s22s22p6
C. The correct electron configuration for calcium is
1) 1s22s22p63s23p63d2
2) 1s22s22p63s23p64s2
3) 1s22s22p63s23p8
Learning Check

107
A. The correct electron configuration for nitrogen is
3) 1s22s22p3
B. The correct electron configuration for oxygen is
2) 1s22s22p4
C. The correct electron configuration for calcium is
2) 1s22s22p63s23p6s2
Solution

108
Write the electron configuration and abbreviated configuration for each of the following elements:
A. Cl
B. S
C. K
Learning Check

109
A. Cl
1s22s22p63s23p5 [Ne]3s23p5
B. S
1s22s22p63s23p4 [Ne]3s23p4
C. K
1s22s22p63s23p64s1 [Ar]4s1
Solution

110
Sublevel Blocks on the Periodic Table
The periodic table consists of sublevel blocks
arranged in order of increasing energy.
Groups 1A(1) to 2A(2) = s level
Groups 3A(13) to 8A(18) = p level
Groups 3B(3) to 2B(12) = d level
Lanthanides/Actinides = f level

111
Sublevel Blocks

112
Using Sublevel Blocks
To write a configuration
using sublevel blocks
Locate the element on the periodic table.
Starting with H in 1s, write each sublevel block in order going left to right across each period.
Write electrons for each block.

113
Using the periodic table, write the electron configuration
for silicon.
Solution:
Period 1 1s block 1s2
Period 2 2s → 2p blocks 2s2 2p6
Period 3 3s → 3p blocks 3s23p2 (at Si)
Writing all the sublevel blocks in order gives:
1s22s22p63s23p2
Writing Electron Configurations

114
The 4s orbital has a lower energy than the 3d orbitals.
In potassium (K), the last electron enters the 4s orbital instead of the 3d (as shown below).
1s 2s 2p 3s 3p 3d 4s
Ar 1s2 2s22p6 3s23p6
K 1s2 2s22p6 3s23p6 4s1
Ca 1s2 2s22p6 3s23p6 4s2
Sc 1s2 2s22p6 3s23p6 3d1 4s2
Ti 1s2 2s22p6 3s23p6 3d2 4s2
Electron Configurations of the d Level

115
Using the periodic table, write the electron configuration
for manganese.
Solution:
Period 1 1s block 1s2
Period 4 4s → 3d blocks 4s2 3d5 (at Mn)
Writing all the sublevel blocks in order gives:
1s22s22p63s23p64s23d5
Writing Electron Configurations

116
4s Block

117
3d Block

118
4p Block

119
A. The last two sublevel blocks in the electron
configuration for Co are
1) 3p64s2
2) 4s24d7
3) 4s23d7
B. The last three sublevel blocks in the electron
configuration for Sn are
1) 5s25p24d10
2) 5s24d105p2
3) 5s25d105p2
Learning Check

120
A. The last two sublevel blocks in the electron
configuration for Co are
3) 4s23d7
B. The last three sublevel blocks in the electron
configuration for Sn are
2) 5s24d105p2
Solution

121
Using the periodic table, write the electron configuration and abbreviated configuration for each of the following elements:
A. Zn
B. Sr
C. I
Learning Check

122
A. Zn
1s22s22p63s23p64s23d10
[Ar]4s23d10
B. Sr
1s22s22p63s23p64s23d104p65s2
[Kr]5s2
C. I
1s22s22p63s23p64s23d104p65s24d105p5
[Kr]5s24d105p5
Solution

123
Learning Check
Give the symbol of the element that has
A. the abbreviated configuration [Ar]4s23d6
B. four 3p electrons
C. two electrons in the 4d sublevel
D. the electron configuration
1s22s22p63s23p64s23d2

124
Solution
Give the symbol of the element that has
A. the abbreviated configuration [Ar]4s23d6 Fe
B. four 3p electrons S
C. two electrons in the 4d sublevel Zr
D. the electron configuration Ti
1s22s22p63s23p64s23d2

125
3.8 Periodic Trends

126
Valence Electrons
The valence electrons
determine the chemical properties of the elements
are the electrons in the outermost, highest energy level
are related to the Group number of the element
Example: Phosphorus has 5 valence electrons.
5 valence
electrons
P Group 5A(15) 1s22s22p63s23p3

127
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 1s22s2
Mg 1s22s22p63s2
Ca [Ar]4s2
Sr [Kr]5s2
Groups and Valence Electrons

128
Periodic Table and Valence Electrons

129
State the number of valence electrons for each.
A. O
1) 4 2) 6 3) 8
B. Al
1) 13 2) 3 3) 1
C. Cl
1) 2 2) 5 3) 7
Learning Check

130
A. O
2) 6
B. Al
2) 3
C. Cl
3) 7
Solution

131
A. Calcium
1) 1 2) 2 3) 3
B. Group 6A (16)
1) 2 2) 4 3) 6
C. Tin
1) 2 2) 4 3) 14
Learning Check

132
A. Calcium
2) 2
B. Group 6A (16)
3) 6
C. Tin
2) 4
Solution

133
A. 1s22s22p63s23p1
B. 1s22s22p63s2
C. 1s22s22p5
Learning Check

134
A. 1s22s22p63s23p1 3
B. 1s22s22p63s2 2
C. 1s22s22p5 7
Solution

135
Electron-Dot Symbols
An electron-dot symbol
indicates valence electrons
as dots around the symbol of the element
of Mg shows two valence electrons as single dots on the sides of the symbol Mg
· ·
· Mg · or Mg · or · Mg or · Mg
·

136
Writing Electron-Dot Symbols
The electron-dot symbols for
Groups 1A(1) to 4A(14) use single dots
· ·
Na · · Mg · · Al · · C ·
·
Groups 5A(15) to 7A(17) use pairs and single dots.
· · · ·
· P · : O ·
· ·

137
Groups and Electron-Dot Symbols
in a group, all the electron-dot symbols have the same number of valence electrons (dots).
Example: Atoms of elements in Group 2A(2) each have 2 valence electrons.
2A(2)
· Be ·
· Mg ·
· Ca ·
· Sr ·
· Ba ·

138

A. X is the electron-dot symbol for
1) Na 2) K 3) Al
 
B.  X  is the electron-dot symbol for

Learning Check
1) B 2) N 3) P

139
Solution

A. X is the electron-dot symbol for
1) Na 2) K
 
B.  X  is the electron-dot symbol for

2) N 3) P

140
Atomic Size
Atomic size
is described using the atomic radius
is the distance from the nucleus to the valence electrons
increases going down a group
decreases going across a period from left to right

141
Atomic Size (continued)

142
Atomic Radius Within A Group
Atomic radius
increases going down a group

143
Learning Check
Select the element in each pair with the larger atomic
radius.
A. Li or K
B. K or Br
C. P or Cl

144
Solution
Select the element in each pair with the larger atomic radius.
A. K is larger than Li
B. K is larger than Br
C. P is larger than Cl

145
Ionization Energy
Ionization energy
is the energy it takes to remove a valence electron from an atom in the gaseous state
Na(g) + Energy (ionization) Na+(g) + e–

Ionization Energy and Valence Electrons
Ionization energy
decreases going down a group as the distance between the nucleus and valance electrons increases
146

147
Ionization Energy
The ionization
energies of
metals are low
nonmetals are high

148
Learning Check
Select the element in each pair with the higher
ionization energy.
A. Li or K
B. K or Br
C. P or Cl

149
Solution
Select the element in each pair with the higher
ionization energy.
A. Li is higher than K
B. Br is higher than K
C. Cl is higher than P

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