Slide 1
UNIT 5: THE PERIODIC
TABLE
Slide 2
Organizing the Elements
How would you organize the people in this room?
How did chemists begin to organize the known elements?
Slide 3
Organizing the Elements
For example, chlorine, bromine, and iodine have very similar chemical properties. It would make
sense to group them together.
Slide 4
Organizing the Elements
In 1869, Dmitri Mendeleev published a table of the elements.
Mendeleev arranged the elements in his periodic table in order if increasing atomic mass.
Slide 5
Organizing the Elements
The periodic law: When elements are arranged in order of
increasing atomic number, there is a periodic repetition of
their physical and chemical properties.
In the modern periodic table, elements are arranged in order of increasing atomic number.
The rows in the periodic table are called periods. The columns in the periodic table are called
groups.
The properties of the elements within a period change as you move from left to right.
The pattern of properties within a period repeats as you move from one period to the next.
Slide 6
Organizing the Elements
The three classes of elements are metals, nonmetals, and metalloids.
Slide 7
Organizing the Elements
Metals are good conductors of heat and electric current.
80% of elements are metals
Metals have a high luster, are ductile, and are malleable
The gateway arch in St. Louis, MO is covered in stainless steel, which is iron, chromium, and
nickel. The steel is shiny, malleable, and strong. It also resists rusting.
Copper is ductile and second to only silver as a conductor of electric current. The copper used in
electrical cables must be 99.99% pure.
Aluminum is one of the metals that can be shaped into a thin sheet, or foil. To qualify as a foil, a
metal must be no thicker than about 0.15 mm.
Slide 8
Organizing the Elements
In general, nonmetals are poor conductors of heat and
electric current.
Most nonmetals are gases at room temperature
A few nonmetals are solids, such as sulfur and phosphorus.
One nonmetal, bromine, is a dark-red liquid
Slide 9
Organizing the Elements
A metalloid generally has properties that are similar to
those of metals and nonmetals.
The behavior of a metalloid can be controlled by changing conditions.
For example, silicon (Si) and germanium (Ge) are good insulators at low temperatures and good
conductors at high temperatures
Slide 10
Classifying the Elements
The elements in groups 1A through 7A are called the
representative elements.
The group number equals the number of valence
electrons in an element in that group.
• Valence electrons are the electrons in the highest
occupied energy level of an atom.
The s and p sublevels of the highest occupied energy level are not filled
Slide 11
Classifying the Elements
The elements in Group 1A are called the alkali metals.
The elements in Group 2A are called the alkaline earth
metals.
The elements in Group 7A of the periodic table are called
the halogens.
The noble gases are the elements in Group 8A of the
periodic table.
All have one valence electron.
The metals in Group 1A are the most reactive metals in the periodic table.
Only found in compounds in nature.
Reactivity increases as you move down the group.
All have two valence electrons.
The metals in Group 2A are less reactive than the metals in Group 1A.
Reactivity also increases as you move down the group.
Each element has seven valence electrons.
The halogens are the most reactive nonmetals.
The reactivity decreases as you move down the group.
The s and p sublevels of the highest occupied energy level is completely filled in each noble gas.
Except helium, each noble gas has eight valence electrons.
The noble gases are inactive elements. They do not normally react with other elements in the
periodic table.
Slide 12
Classifying the Elements
The elements in the middle of the periodic table are called
the transition metals, or sometimes the Group B
elements.
The two rows shown at the bottom of the periodic table
are called the inner transition metals.
In atoms of transition metals, the highest occupied s sublevel and a nearby d sublevel contain
electrons.
In atoms of inner transition metals, the highest occupied s sublevel and a nearby f sublevel
contain electrons.
Slide 13
Periodic Trends
What is the underlying cause of periodic trends?
Coulombic attraction: the attraction between oppositely
charged particles
As you move from left to right across the periodic table, Coulombic attraction increases due to
an increase in nuclear charge (# of protons)
As you move down a group, Coulombic attraction decreases due to an increase in the distance
between the outermost electrons and the nucleus.
Slide 14
Periodic Trends
What are the trends among the elements for atomic size?
In general, atomic size increases from top to bottom within
a group and decreases from left to right across a period?
Slide 15
Periodic Trends
Slide 16
Periodic Trends
How do ions form?
Positive and negative ions form when electrons are
transferred between atoms.
Slide 17
Periodic Trends
How do ions form?
Positive and negative ions form when electrons are
transferred between atoms.
Slide 18
Periodic Trends
Some compounds are composed of particles called ions.
• An ion is an atom or group of atoms that has a positive or
negative charge.
• A cation is an ion with a positive charge.
• An anion is an ion with a negative charge.
Slide 19
Periodic Trends
Cations are always smaller than the atoms from which they
form.
Anions are always larger than the atoms from which they
form.
This is due to an increase in coulombic attraction due to a decrease in the number of electrons
(less repulsion)
This is due to a decrease in coulombic attraction due to an increase in number of electrons
(more repulsion)
Size generally increases
Slide 20
Periodic Trends
Slide 21
Periodic Trends
The energy required to remove an electron from an atom is
called ionization energy.
First ionization energy tends to decrease from top to
bottom within a group and increase from left to right across
a period.
The energy required to remove the first electron from an atom is called the first ionization
energy.
The energy required to remove an electron from an ion with a 1+ charge is called the second
ionization energy.
Slide 22
Periodic Trends
Slide 23
Periodic Trends
Electronegativity is the ability of an atom of an element to
attract electrons when the atom is in a compound.
In general, electronegativity values decrease from top to bottom within a group. For the
representative elements, the values tend to increase from left to right across a period.