UNIT 5: THE PERIODIC
TABLE
Organizing the Elements
How would you organize the people in this room?
How did chemists begin to organize the known elements?
Organizing the Elements
Organizing the Elements
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.
Organizing the Elements
Organizing the Elements
Metals are good conductors of heat and electric current.
Organizing the Elements
In general, nonmetals are poor conductors of heat and
electric current.
Organizing the Elements
A metalloid generally has properties that are similar to
those of metals and nonmetals.
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.
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.
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.
Periodic Trends
What is the underlying cause of periodic trends?
Coulombic attraction: the attraction between oppositely
charged particles
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?
Periodic Trends
Periodic Trends
How do ions form?
Positive and negative ions form when electrons are
transferred between atoms.
Periodic Trends
How do ions form?
Positive and negative ions form when electrons are
transferred between atoms.
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.
Periodic Trends
Cations are always smaller than the atoms from which they
form.
Anions are always larger than the atoms from which they
form.
Size generally increases
Periodic Trends
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.
Periodic Trends
Periodic Trends
Electronegativity is the ability of an atom of an element to
attract electrons when the atom is in a compound.