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Periodic Table of the Elements Notes
Arrangement of the known elements based on atomic number and chemical and physical properties.
Divided into three basic categories:
Metals (left side of the table)
Nonmetals (right side of the table)
Metalloids (touching the zig zag line)
Basic Organization by:
Atomic structure
Atomic number
Chemical and Physical Properties
Uses of the Periodic Table
Useful in predicting:
chemical behavior of the elements
trends
properties of the elements
Atomic Structure Review:
Atoms are made of protons, electrons, and neutrons.
Elements are atoms of only one type.
Elements are identified by the atomic number (# of protons in nucleus).
Energy Levels Review:
Electrons are arranged in a region around the nucleus called an electron cloud. Energy levels are located
within the cloud.
At least 1 energy level and as many as 7 energy levels exist in atoms
Energy Levels & Valence Electrons
Energy levels hold a specific amount of electrons:
1st level = up to 2
2nd level = up to 8
3rd level = up to 8 (first 18 elements only)
The electrons in the outermost level are called valence electrons.
Determine reactivity - how elements will react with others to form compounds
Outermost level does not usually fill completely with electrons
Using the Table to Identify Valence Electrons
Elements are grouped into vertical columns because they have similar properties.
These are called groups or families.
Groups are numbered 1-18.
Group numbers can help you determine the number of valence electrons:
Group 1 has 1 valence electron.
Group 2 has 2 valence electrons.
Groups 3–12 are transition metals and have 1 or 2 valence electrons.
Groups 13–18 have 10 fewer than the group number. For example:
Group 1 3 has 3 valence electrons.
Group 1 5 has 5 valence electrons.
Group 1 8 has 8 valence electrons (except He)
Elements & Reactivity
Reactivity is a chemical property that determines how elements will react with others to form
compounds.
What makes an element reactive?
● Number of valence electrons of each atom
● When outer levels are full, atoms are stable.
● When they are not full, they react:
● gain, lose, or share 1 or 2 electrons
The most reactive metals are the elements in Groups 1 and 2.
Elements in Group 1 generally lose an electron so their outer energy level is empty.
Elements in Group 2 generally lose two electrons so their outer energy level is empty.
These groups easily give up their valence electrons to make a compound.
The most reactive nonmetals are the elements in Groups 16 and 17.
Elements in Group 16 need two more electrons to fill their outer energy level.
Elements in Group 17 need one more electron to fill their outer energy level.
These groups gain valence electrons to make a compound.
Groups
Groups run vertically in the periodic table.
They are numbered from 1–18.
Elements in the same groups have the same number of valence electrons in the outer energy level.
Grouped elements behave chemically in similar ways.
Groups 3-12 Rare Earth Elements ~ Actinides
Actinides follow the transition metal atomic number 89 Actinium in Period 7
Valence electrons: 3 (but up to 6)
Reactivity: unstable
All are radioactive
Most made in laboratories
Metalloids
A zig-zag line that separates metals from metalloids
Elements from Groups 13–16 contain some metalloids.
Metalloids are Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium and Polonium
These elements have characteristics of metals and nonmetals.
Group 13: Boron Group
Group 13: Boron Group
Contains: 1 metalloid and 4 metals
Valence Electrons: 3
Reactivity: Reactive
Other shared properties:
Solid at room temperature
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Periods run horizontally across the Periodic Table
Periods are numbered 1– 7
All the elements in a period will have the same number of energy levels, which contain electrons.
Examples:
Period 1 atoms have 1 energy level.
Period 2 atoms have 2 energy levels.
Period 5 atoms have 5 energy levels.
