Valence
Electrons
STANDARD 1D
Students know how to use the periodic table to determine
the number of electrons available for bonding.
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WHY ARE VALENCE
ELECTRONS
IMPORTANT?
Review…
• Protons and
Neutrons are in the
nucleus
• Electrons are
located in energy
levels (shells) that
surround the
nucleus
• Electrons in the outer shell of an atom are
responsible for chemical bonds!
• If an outer shell holds 8 valence electrons – no
bonding will take place!
Valence Electrons
• Electrons are arranged
around the nucleus in 7
specific areas called
energy levels.
• The valence electrons
participate in the
formation of chemical
bonds.
• Valence electrons are the
outermost electrons.
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1
2
3
4
5
6
E7
E5
7
E3
E2
E1
nucleus
E4
E6
How to Determine Valence
Electrons
• You can determine how many valence electrons
an element has by determining which group it is
in.
1
8
2
3
2
4
5
6
7
Octet Rule
• Elements with 8 valence electrons have a full
outer shell and will not bond! (Noble Gases)
• 8 outer electrons is the ideal number of
valence electrons that all atoms seem to want.
• All elements want to be stable like the noble
gases (have 8 electrons in their outer shells).
Valence Electrons and Bonding
• The only electrons available
for bonding with other atoms
are the outermost electrons.
Only
These
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• The number of outer or valence
electrons can be determined by
their location on the periodic table.
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Noble Gases and Bonding
• (Group 18 or 8A) = 8 valence electrons
• Do not react with other atoms (inert).
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8
e
“We don’t want to bond
with anyone!”
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• Helium only has 2
electrons.
• Helium only has 1 energy
level.
• The 1st energy level can
only hold 2 electrons!
• Thus, helium has a full
outer shell.
Alkali Metals and Bonding
• One valence
electron available for
bonding.
• These metals readily
give this electron to
another atom to
form an ionic bond.
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“Please take my electron! I really want
- to look like a Noble Gas!”
1e
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Alkaline Earth Metals and Bonding
• Two valence electrons for bonding.
• Gives 2 electrons away to form ionic
bonds.
15
“My two electrons need to go, because
my second to last shell is full!”
2 e-
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Transition Metals and Bonding
• Most have 2 valence electrons.
• These metals often give these electrons to
another atom to form an ionic bond.
• Utilize another
process to find the
ve-
17
“Some transition elements are found
free in nature while others give 2
electrons!”
2e-
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The Halogens and Bonding
• Group 17 or 7A = seven valence electrons.
• These nonmetals often take one electron
from another atom to form an ionic bond.
19
“Gaining one electron will make my
valence 8! So you better watch out
cause your electron I will take!”
7 e-
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Lewis Dots
• Also known as electron dot diagrams
• Useful tool for determining how an element
will bond
• Includes the element symbol and a group of
1-8 dots which shows the configuration of
the outer-most electron shell of the atom,
also called the valence shell.
21
Lewis Dot Examples