Download Unit 3 Lesson 2 The Periodic Table Essential Question: How are

Unit 3 Lesson 2 The Periodic Table
Essential Question: How are elements
arranged on the periodic table?
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Unit 3 Lesson 2 The Periodic Table
p170
Get Organized!
What are elements?
• By the 1860s, scientists considered there to be at
least 60 different basic substances, or elements.
• Scientists found that many of these elements have
similar properties and began classifying them.
Unit 3 Lesson 2 The Periodic Table
What are elements?
p170
Get Organized!
dull, nonmetal, brittle, odor
Solid, shiny, metal
gas, nonmetal, yellow
liquid, shiny, metal
metal, shiny
Liquid, nonmetal
Unit 3 Lesson 2 The Periodic Table
p171
How are the elements organized?
• Dmitri Mendeleev first organized the elements by
arranging them in order of increasing atomic mass.
• He observed that the properties of those elements were in
a periodic, or regularly repeating, pattern.
Unit 3 Lesson 2 The Periodic Table
p171
How are the elements organized?
• Mendeleev’s arrangement of the elements became known
as the periodic table.
• Henry Moseley reorganized Mendeleev’s periodic table
in order of increasing number of protons, or atomic
number.
• The periodic table is useful because it makes clear many
patterns among the elements’ properties.
6) Explain
Henry Moseley arranged the
elements on the periodic table in
order of increasing atomic
number
Unit 3 Lesson 2 The Periodic Table
P172-173
How are the elements organized?
8) 3
9) 6
Unit 3 Lesson 2 The Periodic Table
p174
Making Arrangements
What information is contained in each
square on the periodic table?
• Each square contains an element’s chemical name,
atomic number, chemical symbol, and average atomic
mass.
• The atomic number is placed at the top of each square.
• The chemical symbol is an abbreviation for the
element’s name.
• The first letter of the chemical symbol is always
capitalized, and any other letter is lowercase.
• The name of the element is written under the symbol.
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p174
Unit 3 Lesson 2 The Periodic Table
p174
What information is contained in each
square on the periodic table?
• All atoms of an element have the same number of
protons, but the number of neutrons can vary.
• The average atomic mass of an atom is the
weighted average of the masses of all the
naturally occurring isotopes of that element.
• Average atomic mass is reported in atomic mass
units (u).
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Unit 3 Lesson 2 The Periodic Table
p175
How are the elements arranged on the
periodic table?
• A zigzag line on the periodic table divides the
three major categories of elements: metals,
nonmetals, and metalloids.
• Metals are elements that are shiny and conduct
heat and electricity well.
• Elements to the left of the zigzag line are metals,
except for hydrogen.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 2 The Periodic Table
p175
How are the elements arranged on the
periodic table?
• The elements to the right of the zigzag line are
nonmetals.
• Nonmetals are poor conductors of heat and
electricity, and are often dull and brittle.
• Metalloids are elements that have some
properties of metals and nonmetals. They border
the zigzag line.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 2 The Periodic Table
p175
How are the elements arranged on the
periodic table?
• List three metals, nonmetals, and metalloids.
Copyright © Houghton Mifflin Harcourt Publishing Company
Unit 3 Lesson 2 The Periodic Table
p176
How are the elements arranged on the
periodic table?
• Each vertical column of
elements on the periodic table
is called a group, or family.
• Elements in a group are similar
because their atoms have the
same number of valence
electrons.
• Valence electrons participate in
chemical bonding.
Unit 3 Lesson 2 The Periodic Table
p177
How are the elements arranged on the periodic
table?
• Each horizontal row of elements on
the periodic table is called a period.
• Physical and chemical properties of
elements change in predictable ways
from one end of the period to the
other.
• Elements in the same period have the
same number of energy levels
•Atomic number increases as you move from left to
right
•Number of energy levels increase by 1 as you go down
the periodic table
•Number of Valence Electrons increase and you go from
left to right on the periodic table
•Atomic size decreases as you move from left to right
•Atomic number increases as you move from left to
right
•Number of energy levels increase by 1 as you go down
the periodic table
•Number of Valence Electrons increase and you go from
left to right on the periodic table
•Atomic size decreases as you move from left to right
across a period.
Al
13
13
13
Atomic number and # of p+ are equal
e- and # of p+ are equal
2
Protons
Electrons
Atomic Number
3
3
How many energy levels are in the atom
Ar
C
He
Li
O
S
Si
Na
18
6
2
3
8
16
14
11
18
6
2
3
8
16
14
11
18
6
2
3
8
16
14
11
3
2
1
2
2
3
3
3
3
2
1
2
2
3
3
3
2
1
2
3
3
2
1
2
3
3
4
2
1
4
1
18
14
18
1
14
1
Same number of valence electrons
Same number of energy levels or shells
17
2
3
3
7
17
2
3
6
1
group
period
Atomic Number
Protons
Valence electrons
Energy levels (shells)
Down
Across
Vertical
Horizontal
2) Describe the pattern you see in the graph
The line drops steadily and then jumps and begins to drop
again in a diagonal line pattern
3) Compare your graph to the periodic table of elements. How
does the pattern relate to the structure in the periodic table?
The diagonal line in the graph relate to the periods (rows)
in the periodic table.
Each jump in the line marks the beginning of a new period
(row) in the periodic table
4) What trends to you observe about the relationship between
atomic radius and the atomic number?
The value for atomic radii generally decrease across a
period and increase down a group.
5) Based on the trends, what are approximate values of the
atomic radii of 10, 18, and 31
50, 90, 150