Transcript Ionic Compounds Intro

Ionic Compounds
and their Properties
What are Ionic Compounds
Ionic compounds are compounds that are
composed of cations (positively charged
ions) and anions (negatively charged
ions).
 They usually involve a metal (forms the
cation) and a nonmetal (anion)

What causes atoms to form
ions?




Every element wants to be like a noble gas and
have 8 valance electrons (Rule of octet).
Elements will form chemical bonds to have 8 by
either sharing or transferring electrons.
Ionic bonds deal with the transfer of electrons
and the attractive forces between the opposite
charged ions that form.
Every element that is close to having 8 valance
electrons will steal or give away electrons to get
to 8.
So, it boils down to stability
Atoms can form multiple ions based on the
stability of their electron configurations.
 The charges are known as the ion’s
oxidation numbers.
 Remember, only ions have oxidation
numbers. All atoms, elements, molecules,
and compounds have an oxidation number
of zero. (They are overall neutral)
 Ions can have oxidation numbers ranging
from -4 to +7.

Let’s look at Na and Cl

What is the electron configuration of Na?
1s2 2s2 2p6 3s1 or [Ne] 3s1

How can Na become like a noble gas?

It can lose an electron.

What is the electron configuration of Cl?
1s2 2s2 2p6 3s2 3p5 or [Ne] 3s2 3p5

How can Cl become like a noble gas?

It can gain an electron
Let’s look at Na and Cl

Na becomes
What is the electron configuration of Na? Na+ and
more stable
1s2 2s2 2p6 3s1 or [Ne]

How can Na become like a noble gas?


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It can lose an electron.
What is the electron configuration of Cl?
1s2 2s2 2p6 3s2 3p5 or [Ne] 3s2 3p6
How can Cl become like a noble gas?

It can gain an electron
[Ar]
Cl becomes
Cl- and more
stable
This can also be done
with Lewis Dot
Formulas
So, let’s practice that…
(back of homework from last
class)
To find the oxidation number of the ions that
compose an ionic compound, remember…
The elements from group 1 will be +1,
group 2 will be +2, group 13 will be +3,
group 15 will be -3, group 16 will be -2,
and group 17 will be -1. The transitional
elements vary.
 When dealing with two atoms, the first
atom listed will have a positive number,
the second will have a negative number.
 The sum of the charges times their
subscripts must equal zero.

What column does every element want to be like?
Most Common Predicted Oxidation Numbers
0
+1
+2
+3
vary
-3 -2 -1
Find the oxidation number for each
atom in the following molecules
NaCl
 MgO
 WS3
 AlN
 ZnBr2
 PCl5
 HgS

+1
 +2
 +6
 +3
 +2
 +5
 +2

-1
-2
-2
-3
-1
-1
-2
Homework
Page 165: 6,7,10,11,13 and
Page 183: 7,9,12,13,16