Chapter 5 –
The Periodic
Table
5.1 Organizing the Elements
Antoine Lavoisier (1743-1794)
• the Father of Modern Chemistry
• In 1789, he grouped the elements into
categories
- metals
- nonmetals
- gases
- earths
• for 80 years scientists tried to classify elements, but no one
way accounted for the variety of elements known
5.1 Organizing the Elements
Dmitri Mendeleev (1834-1907)
• a chemist and teacher
• by the 1860’s, there were 63 known
elements
• used the game of
solitaire as the inspiration
for his organization of the
elements
5.1 Organizing the Elements
• on each card, he listed the
element’s name, mass and
properties
• lined up cards in rows in order
of increasing mass
• kept elements with similar
properties in the same column
• the chart was periodic
(repeating)
5.1 Organizing the Elements
periodic table – an arrangement of elements in columns,
based on a set of properties that repeat from row to row
5.1 Organizing the Elements
• Some elements would not fit in certain spots because
they didn’t have the right mass and / or properties
• Mendeleev left gaps in the table
5.1 Organizing the Elements
• Mendeleev went on to give names to elements he predicted
would be discovered and fill in the blanks
• Named a predicted element “eka-aluminum”
• Later an element was discovered that matched the
properties of eka-aluminum. (named Gallium)
• With a periodic table the chemical behavior of elements can
be explained and predicted
5.2 The Modern Periodic Table
• In the modern periodic table, elements are arranged by
increasing atomic number (number of protons)
5.2 The Modern Periodic Table
• each row is called a period
• the number of elements per period varies because the
number of available orbitals varies
5.2 The Modern Periodic Table
• each column is called a group
• the elements within a group have similar properties
• the pattern of repeating properties is the periodic law
5.2 The Modern Periodic Table
atomic number
1
element symbol
H
Hydrogen
1.0079
element name
atomic mass
atomic mass unit (amu) – one twelfth the mass of a
carbon-12 atom
5.2 The Modern Periodic Table
17
What is the atomic mass of chlorine?
35.453 amu
Cl
Chlorine
35.453
Distribution of Chlorine
Isotopes in Nature
Isotope
Percentage
Atomic Mass
Chlorine-35
75.78%
34.969
Chlorine-37
24.22%
36.966
• the atomic mass is a weighted average of these values
5.2 The Modern Periodic Table
5.2 The Modern Periodic Table
• elements are first
classified as solids,
liquids, or gases
5.2 The Modern Periodic Table
• elements are then classified as to whether or not they
occur naturally
• all but two elements in the first 92 elements occur
naturally
5.2 The Modern Periodic Table
• then classified as metals, nonmetals, and metalloids
5.2 The Modern Periodic Table
• most of the elements are metals
- good conductors
- malleable and ductile
- solid at room temperature (except Mercury) - some very reactive
5.2 The Modern Periodic Table
• transition metals are groups 3 through 12
• tend to form compounds with distinctive colors
5.2 The Modern Periodic Table
• other elements are called nonmetals
- poor conductors
- the solids are brittle
- many are gases at room temperature
- some are reactive, some aren’t
5.2 The Modern Periodic Table
• and still other elements are called metalloids
- properties of metals and nonmetals
- conductivity varies with temperature
5.2 The Modern Periodic Table
• elements become less metallic and more nonmetallic
going across a period from left to right
5.3 Representative Groups
Is hydrogen a metal?
It is not. Why, then, is it grouped with the metals in the
periodic table?
It shares an electron configuration similar to other elements
in Group 1
5.3 Representative Groups
The number of the A groups tells the number of valence
electrons in an atom.
valence electron – an electron in the highest energy level
of an atom
Elements in groups share properties because they have
the same number of valence electrons
5.3 Representative Groups
Group 1A – Alkali Earth Metals
1. One valence electron
2. Found in nature as compounds
3. Reactivity increases going from top to bottom
of group
4. Many react violently with water
5. Very soft (can cut with a knife)
Video 1
Video 2
Video 3
Video 4
Video 5
Video 6
5.3 Representative Groups
Group 2A – Alkaline Earth Metals
1. Two valence electrons
2. Harder than Group 1A elements
GROUPS 3 – 12:
TRANSITION METALS
• Contain many everyday metals
• Metal properties as listed earlier
Au - Gold
Ag - Silver
INNER TRANSITION METALS
• rare in nature
• all solids
• Similar properties across the period
rather than down a group
5.3 Representative Groups
Group 3A – Boron Family
1. Three valence electrons
2. Aluminum is the most abundant metal in the
Earth’s crust
5.3 Representative Groups
Group 4A – Carbon Family
1. Four valence electrons
2. Get more metallic as go down group
3. Most compounds in the body contain carbon
(the exception is H2O)
4. Silicon is the 2nd most abundant element in
the Earth’s crust
5.3 Representative Groups
Group 5A – Nitrogen Family
1. Five valence electrons
2. 78% of the atmosphere is nitrogen
5.3 Representative Groups
Group 6A – Oxygen Family
1. Six valence electrons
2. Oxygen is the most abundant element in the
Earth’s crust
3. Sulfur was one of the first element’s
discovered
5.3 Representative Groups
Group 7A – The Halogens
1. Seven valence electrons
2. All are highly reactive
3. React with most metals and many
non-metals
• non-metals
• strong unpleasant odor and will burn flesh
• do not dissolve well in water
5.3 Representative Groups
Group 8A – The Noble Gases
1. Eight valence electrons, except Helium
(has 2)
2. Colorless, odorless
3. Extremely unreactive
• under normal conditions they do not
form compounds with other elements
4. Used in “neon” lighting