Ionic Bonds form when the difference
in electronegativities between atoms
trying to share electrons is so great, the
electron pair is “stolen” by the more
electronegative of the pair.
The “victim” becomes a positive ion
and the “thief” becomes a negative ion.
Since opposite charged ions attract they
are held together by an ionic bond.
++
+
Li
+
+ +
+ + +
+ +
+
F
++
+
Li
1+
+
+ +
+ + +
+ +
+
F
1-
+
+ +
+ + +
+ +
+
++
+
1+ 1-
Li F
Here is a very
small portion of a
crystal of lithium
fluoride.
When other layers
are added these are
the result.
Ionic solids have this type of 3 dimensional
arrangement.
This is what table salt looks like under a
microscope.
If ionic crystals are placed in water the water
molecules pull apart the crystals forming mobile
ions.
If an conductivity apparatus is placed in a
solution containing ions, the light bulb will
go on.
Sometimes the only way to
tell for certain if a
substance is made up of
ions or molecules is to
dissolve the material in
water and then test with a
conductivity apparatus.
Formation of ions from neutral atoms
occurs because the ions are more stable.
In most instances the ions have electron
arrangements of noble gases.
The way atoms of different elements
combine is determined by the number of
electrons required for each to become
more stable.
Alkali metals combine with halogens in
1:1 ratios since alkali metals need to lose
1 e1- and halogens need to gain 1e1-.
Alkaline earth metals combine with
halogens in 1:2 ratios since alkaline earth
metals need to lose 2 e1- and halogens
need to gain 1e1-.
2e1- Be
2e1- F
7e1-
2e1- F
7e1-
2e1-
Alkaline earth metals combine with
halogens in 1:2 ratios since alkaline earth
metals need to lose 2 e1- and halogens
need to gain 1e1-.
1F
8e1-
2e1- F 1-
8e1-
2e12e1-
2+
Be
Alkaline earth metals combine with
halogens in 1:2 ratios since alkaline earth
metals need to lose 2 e1- and halogens
need to gain 1e1-.
1F
8e1-
2e1- F 1-
8e1-
2e1-
BeF2
2e1-
2+
Be
Lewis Structures can be used to illustrate the
formation of ionic bonds.
1-
Be
+
2 F
F
[Be]2+ F
1-
Write an equation with Electron Dot Diagrams
to illustrate the formation of aluminum
chloride.
1-
Al
+
3
Cl
Cl
[Al]3+
Cl
1-
1-
Cl
Questions - pg. 73,74 # 8-14