Transcript Chapter 5 The Periodic Table

Chapter 5 The Periodic
Table
•Section 5.1 Organizing the
Elements
•Section 5.2 The Modern Periodic
Table
•Section 5.3 Representative Groups
Section 5.1 Organizing
the Elements
• The Search for Order
• The placement of elements on the
periodic table reveals the link
between the atomic structure of
elements and their properties.
Section 5.1 Organizing
the Elements
• The Search for Order
• As # of known elements grew, the need to
organize them did also.
• Antoine Lavoisier (1789), French chemist:
grouped known elements into categories:
metals, nonmetals, gases, and earths
• Dmitri Mendeleev, Russian
chemist/teacher: found a way to organize
the elements
Section 5.1 Organizing
the Elements
• Mendeleev’s Periodic Table:
Mendeleev’s Proposal
• Used deck of cards (4 columns);
break the elements into rows
• Key Concept: Mendeleev arranged
the elements into rows in order of
increasing mass so that elements
with similar properties were in the
same column.
Section 5.1 Organizing
the Elements
• Mendeleev’s Proposal
• Periodic table-an arrangement of
elements in columns, based on a set
of properties that repeat from row to
row
Section 5.1: Organizing
the Elements
• Mendeleev’s Prediction
• Some elements that had not been
discovered yet, he left spaces for;
also predicted the properties for
them
Mendeleev’s Table Figure
of 3
Elements (1872)
Section 5.1 Organizing
the Elements
• Evidence Supporting Mendeleev’s
Table
• Key Concept: The close match
between Mendeleev’s predictions
and the actual properties of new
elements showed how useful his
periodic table could be.
Section 5.1 Organizing
the Elements
• Evidence Supporting Mendeleev’s
Table
• With the periodic table, chemists
could do more than predict
properties of new elements
• They could explain the chemical
behavior of different groups of
elements
Section 5.2 The Modern
Periodic Table
• The Periodic Law
• You can use the modern periodic
table to classify elements and to
compare their properties.
• Key Concept: In the modern
periodic table, elements are
arranged by increasing atomic
number (# of protons)
Figure 7
Periodic Table of Elements
Section 5.2 The Modern
Periodic Table
• The Periodic Law: Periods
• Period-each row in the table of
elements
• # of elements per period varies b/c #
of orbitals increases from energy
level to energy level
• Ex. Period 1 (H and He); Period 2 (Li,
Be, B, C, N, O, F, and Ne)
Section 5.2 The Modern
Periodic Table
• The Periodic Law: Groups
• Group-each column on the periodic
table
• Key Concept: Properties of
elements repeat in a predictable
way when atomic numbers are used
to arrange elements into groups.
Section 5.2 The Modern
Periodic Table
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• The Periodic Law: Groups
Elements in group have same
electron configuration
**Electron configuration determines
element’s chemical properties
Members of a group have similar
chemical properties
Periodic law-pattern of repeating
properties
Section 5.2 The Modern
Periodic Table
• Atomic Mass
• Key Concept: Atomic mass is a
value that depends on the
distribution of an element’s isotopes
in nature and the masses of those
isotopes.
Section 5.2 The Modern
Periodic Table
• Atomic Mass: Atomic Mass Units
• To have a simple way to compare
the masses of atoms, scientists
chose 1 isotope to serve as a
standard.
• Assigned 12 atomic units to carbon12 atom (6 protons and 6 neutrons)
• **Atomic mass unit (amu)-one
twelfth of a carbon-12 atom
Section 5.2 The Modern
Periodic Table
• Atomic Mass: Isotopes of Chlorine and
Weighted Averages
• Most elements exist in nature exist as a
mix of 2 or more isotopes.
• 2 natural isotopes of chlorine (Chlorine-35
and Chlorine-37); Chlorine 37 has more
neutrons (greater mass)
• Atomic mass of 35.453; atomic masses of
the isotopes get averaged together
Figure 9
Isotopes of
Chlorine
Section 5.2 The Modern
Periodic Table
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• Classes of Elements
Periodic table- 3 ways to classify
elements
Solids (black), liquids (purple), or gases
(red)
Elements are divided into those that
occur naturally (1-92) and those that
don’t (93 and higher)
Based on general properties: Key
Concept: Elements are classified as
metals, nonmetals, and metalloids.
Periodic Table of Elements
Figure 7
Section 5.2 The Modern
Periodic Table
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• Classes of Elements: Metals (Blue)
Def.-elements that are good conductors of
electric current and heat.
Majority of elements are metals.
Some extremely reactive, some don’t react
easily
Transition metals (Groups 3-12)-elements
that form a bridge b/t the elements on the
left and right sides of the periodic table
Section 5.2 The Modern
Periodic Table
• Classes of Elements: Nonmetals
(Yellow/Orange)
• Have properties opposite of metals
• Def.-elements that are poor
conductors of heat and electric
current
• Have low boiling points=many are
gas at room temp.
Section 5.2 The Modern
Periodic Table
• Classes of Elements: Metalloids
(Green)
• Def.-elements with properties that
fall between those of metals and
nonmetals
• Ability to conduct electric current
varies with temperature.
Section 5.2 The Modern
Periodic Table
• Variation Across a Period
• Key Concept: Across a period (row)
from left to right, the elements
become less metallic and more
nonmetallic in their properties.
• Most reactive metals-left side
• Most reactive nonmetals-right side
Figure 7
Periodic Table of Elements
Section 5.3
Representative Groups
• Valence Electrons
• The # of an A group matches the # of
valence electrons in an electron
configuration for an element in that
group.
• Def.-an electron that is in the highest
occupied energy level of an atom
Section 5.3
Representative Groups
• Valence Electrons
• Valence electrons play a key role in
chemical reactions.
• **Properties vary across a period (row) b/c
the number of valence electrons increases
from left to right.
• Key Concept: Elements in a group have
similar properties because they have the
same number of valence electrons.
Periodic Table of Elements
Figure 7
Section 5.3
Representative Groups
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• The Alkali Metals-Group 1A
Li, Na, K, Rb, Cs, Fr
Have one valence electron
Are extremely reactive; found in
nature only as compounds
Key Concept: The reactivity of
alkali metals increases from the top
of Group 1A to the bottom.
Section 5.3
Representative Groups
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• The Alkaline Earth Metals-Group 2A
Be, Mg, Ca, Sr, Ba, Ra
Have 2 valence electrons
Harder than Group 1A metals
Key Concept: Differences in reactivity
among the alkaline earth metals are shown
by the ways they react with water (ex. Ca,
Sr, Ba-cold water) and (Mg-hot water)
Mg & Ca-essential for biological functions
and provide materials used in construction
and transportation
Section 5.3
Representative Groups
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• The Boron Family-Group 3A
Have 3 valence electrons
B, Al, Ga, In, Tl
Key Concept: Aluminum is the most
abundant metal in Earth’s crust.
Al-car parts, packaging, airplanes
B-glass that does not shatter easily
w/ rapid temp. change (lab
glassware)
Section 5.3
Representative Groups
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• The Carbon Family-Group 4A
C, Si, Ge, Sn, Pb
Have 4 valence electrons
Metallic nature of group increases from
top to bottom (conductivity)
Life on Earth would not exist w/o Carbon
Key Concept: Except for water, most of
the compounds in your body contain
carbon.
Silicon-the 2nd most abundant element in
the Earth’s crust
Section 5.3
Representative Groups
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• The Nitrogen Family-Group 5A
N, P, As, Sb, Bi
Have 5 valence electrons
Includes elements w/ wide range of
physical properties
N & P-most important
Key Concept: Besides nitrogen,
fertilizers often contain phosphorus.
Section 5.3
Representative Groups
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• The Oxygen Family-Group 6A
O, S, Se, Te, Po
Have 6 valence electrons
Key Concept: Oxygen is the most
abundant element in the Earth’s
crust.
Complex forms of life need O to live.
Ex. Oxygen tanks, ozone layer
S-used in fertilizers
Section 5.3
Representative Groups
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• The Halogens-Group 7A
F, Cl, Br, I, At
Have 7 valence electrons
Key Concept: Despite their physical
differences, the halogens have similar
chemical properties. Pg. 144
Highly reactive nonmetals; reactivity
decreases from top to bottom (F)
F-prevents tooth decay, Cl-kills bacteria,
and I-thyroid gland function
Section 5.3
Representative Groups
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• The Noble Gases-Group 8A
He, Ne, Ar, Kr, Xe, Rn
He has 2 valence electrons; all other have
8 valence electrons
Key Concept: The noble gases are
colorless and odorless and extremely
unreactive.
Ex. Argon-light bulbs; all are used in neon
lights except Radon
He-pink, Ne orange-red, Ar-lavender, Krwhite, Xe-blue