PS-2.5
Predict the charge that a
representative element
will acquire according to
the arrangement of
electrons in its outer
energy level.
Vocabulary
1. Ion: a charged atom; charge is
acquired by gaining or losing
electrons
2. Octet rule: in order to become
stable, an atom will gain or lose
valence electrons to get EIGHT
valence electrons
STABLE ATOMS
„ Have
8 valence electrons
„ Exception:
Helium has 2
What if a neutral atom does
NOT have 8 valence electrons?
„ Gain,
lose, or share valence
electrons to GET EIGHT &
become stable!!!
This is a chemical reaction!
„#
Electrons changes
„ # p, n stays the same
How can we predict if an atom
will GAIN or LOSE electrons?
„ If
I’m an atom with one
electron, will it be easier for
me to
„ FIND
SEVEN more?
„ GET RID OF the one?
Charges
„ Electrons
are NEGATIVELY
charged…
„ Lose
one negative charge
„ Result:
„ POSITIVE
(+1) CHARGE
How can we predict if an atom
will GAIN or LOSE electrons?
„ If
I’m an atom with SEVEN
electrons, will it be easier for
me to
„ FIND
ONE more?
„ GET RID OF the SEVEN?
Charges
„ Electrons
are NEGATIVELY
charged…
„ Gain
one negative charge
„ Result:
„ NEGATIVE
(-1) CHARGE
+1
+2
Oxidation
Numbers
+3 ±4 -3 -2 -1
Metals: Tend to LOSE electrons!
0
Nonmetals:
Tend to
GAIN
electrons!
Goes back to those properties of
Metals, Nonmetals, and
Metalloids!
Lewis Dot Diagrams
„
„
Write the symbol for the element
Draw dots around the symbol
One dot for each valence electron of the
neutral atom
„ Start at “3:00” and go clockwise
„
Lewis Dot Diagrams
„
Example:
Lithium has ____ valence electrons
„ One!
„
Li
Lewis Dot Diagrams
„
Example:
Krypton has ____ valence electrons
„ Eight!
„
Kr
Practice!
„
What’s the charge for stable ION of
Chlorine
„ Iodine
„ Sodium
„ Strontium
„ Xenon
„
Practice!
„
What’s the #p,n,e for a stable ION of
Bromine
„ Sulfur
„ Magnesium
„ Arsenic
„ Argon
„
Practice!
„
Draw Lewis Dot Diagrams for
Potassium
„ Nitrogen
„ Fluorine
„ Barium
„ Radon
„ Boron
„