Lesson 19: Noble Gas Envy
•Ions
U1, L19: Ions
10/28
• DQ: How can valence electrons and electronegativity be used to
predict the result of combining two elements?
• ChemCatalyst: When a lithium atom and a fluorine atom meet,
one of them will steal an electron from the other.
1. Predict who takes the electron and who loses it.
2. What effect does the electron transfer have on the charge of each
atom?
3. After electron transfer . . .
a) Li has the same number of electrons as what element?
b) F has the same number of electrons as what element?
You will be able to:
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•
•
explain that an ion is formed when an atom loses or gains
electrons and state the difference between a cation and an
anion
determine the charge on an ion based on an atom’s
placement in the periodic table
explain the relationship between ion charge and valence
electrons
Definitions
• Ion = an atom (or group of atoms) that has a
positive charge (because it lost one or more
electrons) or a negative charge (because it
gained one or more electrons.
• Cation = Positive ion (has lost electrons)
• Anion = Negative ion (has gained electrons)
Charges on ions are predictable
Representing Ions
“Lewis Dot” Representations of Atoms/Ions
Ions tend to “look like” noble gases.
The “Octet Rule” for Ionic Bonding
Wrap Up
•How can valence electrons and electronegativity be used to
predict the result of combining two elements?
– Nonmetal atoms are stronger at pulling electrons, so they
tend to take electrons away from metal atoms.
– When atoms gain or lose electrons, they form ions. Ions are
atoms that carry a net positive or net negative charge.
– When atoms lose electrons, they have a positive charge and
are called cations.
– When atoms gain electrons, they have a negative charge and
are called anions.
– Ions have electron arrangements resembling those of the
noble gas atoms.