Periodic Trends
Elemental Properties and Patterns
Periodic Table
• Periodicity: regular variations (or patterns) of
properties with increasing atomic number. Both
chemical and physical properties vary in a
periodic (repeating) pattern.
• Group: vertical column of elements (“family”)
• Period: horizontal row of elements
Periodic
Table
and
Periodicity
Chemistry: The Periodic Table and Periodicity
1. Who first published the classification of the elements that is the basis of our periodic
table today?
DMITRI MENDELEEV
2. By what property did Mendeleev arrange the elements?
ATOMIC MASS
3. By what property did Moseley suggest that the periodic table be arranged?
ATOMIC NUMBER
4. What is the periodic law?
THE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLY
5. What is a period? How many are there in the periodic table?
A HORIZONTAL ROW IN THE PERIODIC TABLE; 7
6. What is a group (also called a family)? How many are there in the periodic table?
A VERTICAL COLUMN IN THE PERIODIC TABLE; 18
The Periodic Law
• Mendeleev understood the ‘Periodic Law’
which states:
• When arranged by increasing atomic number,
the chemical elements display a regular and
repeating pattern of chemical and physical
properties.
Metals, Nonmetals, & Metalloids
1
Nonmetals
2
3
4
5
Metals
6
7
Metalloids
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 349
Transition metals
lanthanides
actinides
halogens
noble gases
alkali metals
alkaline earth metals
Elements with similar chemical behavior are in the same group.
Metals
• Metals are lustrous
(shiny), malleable,
ductile, and are good
conductors of heat
and electricity.
• They are mostly solids
at room temp.
• What is one
exception?
Mercury
(Hg)
Nonmetals
• Nonmetals are the
opposite.
• They are dull, brittle,
nonconductors
(insulators).
• Some are solid, but
many are gases, and
Bromine is a liquid.
Metalloids
• Metalloids, aka semi-metals
are just that.
• They have characteristics of
both metals and nonmetals.
• They are shiny but brittle.
• And they are
semiconductors.
• What is our most important
semiconductor?
Periodic trends
Identifying the patterns
Metallic Characteristics
metallic character increases
metallic character increases
Periodic
Table
and
Periodicity
Chemistry: The Periodic Table and Periodicity
1. Who first published the classification of the elements that is the basis of our periodic
table today?
DMITRI MENDELEEV
2. By what property did Mendeleev arrange the elements?
ATOMIC MASS
3. By what property did Moseley suggest that the periodic table be arranged?
ATOMIC NUMBER
4. What is the periodic law?
THE PROPERTIES OF THE ELEMENTS REPEAT PERIODICALLY
5. What is a period? How many are there in the periodic table?
A HORIZONTAL ROW IN THE PERIODIC TABLE; 7
6. What is a group (also called a family)? How many are there in the periodic table?
A VERTICAL COLUMN IN THE PERIODIC TABLE; 18
Experiment
Variable –
factor in the
experiment
that is being
tested
• The factor that is changed is known
as the independent variable (IV).
– Also referred as “The Cause”
• The factor that is measured or
observed is called the dependent
variable (DV).
– Also referred as “The Effect”
Rule for Addition and Subtraction
Calculating with Numbers Written in Scientific Notation
In order to add or subtract numbers written in scientific
notation, you must express them with the same power of 10.
Sample Problem: Add 5.8 x 103 and 2.16 x 104
(5.8 x 103) + (21.6 x 103) =
27.4 x 103
Exercise: Add 8.32 x 10-7 and 1.2 x 10-5
2.74 x 104
1.28 x 10-5
http://phet.colorado.edu/en/simulation/balloons
+
-
Particles with opposite
charges attract
one another.
+ +
Particles with like charges
repel one another.
-
Depends on:
2+
1+
2-
1-
• 1. Amount of charge
2+
2+
2-
2-
• 2. Distance between charges
Periodic Trends
• atomic radius.
• Radius is the distance from the center of the
nucleus to the “edge” of the electron cloud.
Atomic Radii
Atomic Radii
• Trend: decreases across a period
WHY???
– As the # of protons in the nucleus increases, the positive
charge increases and as a result, the “pull” on the electrons
increases.
• Trend: increases down a group
WHY???
– The atomic radius gets bigger because electrons are added
to energy levels farther away from the nucleus decreasing
the “pull” or force of attraction.
Atomic Size Trends
Ionization Energy
• Definition: energy required to remove outer electrons from an atom
Hungry for Tater Tots?
Mr. C at 7 years old.
OUCH!!
Ionization Energy
• Trend: increases across a period
• WHY???
• All the atoms in the same period
– Increasing the number of protons increase the
“pull” or force of attraction.
• Trend: decreases down a group
• WHY???
– Electrons are further away from the positive “pull”
of the nucleus and therefore easier to remove.
He
Ne
Ar
First Ionization energy
Kr
H
Li
Na
K
Rb
Atomic number
Electronegativity
• Definition: the tendency of an atom to
attract electrons to itself when chemically
combined with another element
Electronegativity
• Trend: increases across a period
(noble gases excluded!)
• WHY???
– Nuclear charge is increasing, atomic radius is
decreasing; attractive force that the nucleus can
exert on another electron increases.
• Trend: decreases down a group
• WHY???
– The electrons are farther away from the nucleus;
decreased attraction, so decreased
electronegativity
ElectronegativityTrends
Summing Up Periodic Trends
Summing Up Periodic Trends
Which has the largest atomic radius?
7. Br- Br
8. Al+ Al
As an atom gains electrons, the atom gets bigger
As an atom loses electrons, the atom gets smaller