grade 9 - science IONIC BONDING AND STRUCTURE.PPT

Grade 9 science

1. 4.1
IONIC BONDING AND STRUCTURE
By: Merinda Sautel
Alameda Int’l Jr/Sr High School
Lakewood, CO
[email protected]

2. ESSENTIAL IDEA
Ionic compounds consist of ions held
together in lattice structures by ionic
bonds.
NATURE OF SCIENCE (2.2)
Use theories to explain natural phenomena –
molten ionic compounds conduct electricity but
solid ionic compounds do not. The solubility
and melting points of ionic compounds can be
used to explain observations.

3. THEORY OF KNOWLEDGE
General rules in chemistry (like the
octet rule) often have exceptions. How
many exceptions have to exist for a rule
to cease to be useful?
What evidence do you have for the
existence of ions? What is the difference
between direct and indirect evidence?

4. UNDERSTANDING/KEY IDEA
4.1.A
Positive ions (cations) form by
metals losing valence electrons.

5. UNDERSTANDING/KEY IDEA
4.1.B
Negative ions (anions) form by
non-metals gaining electrons.

6. An ion is a charged particle. Ions form when
atoms gain or lose electrons.
A cation is a positive ion.
Formed when an atom loses one or more
electrons.
An anion is a negative ion.
Formed when an atom gains one or more
electrons.
The charge on an ion is equal to the number of
electrons gained or lost.

7. UNDERSTANDING/KEY IDEA
4.1.C
The number of electrons lost or
gained is determined by the
electron configuration of the
atom.

8. CATIONS FROM GROUPS 1, 2 AND 3
Group 1 elements have one valence electron so they
tend to lose one electron and form 1+ ions.
Group 2 elements have two valence electrons so they
tend to lose two electrons and form 2+ ions.
Group 3 elements have three valence electrons so they
tend to lose three electrons and form 3+ ions.
NOTICE THAT FOR IONS, THE CHARGE IS LISTED AFTER
THE NUMBER (2
+
, 3
-
). OXIDATION STATES ARE LISTED
WITH THE CHARGE BEFORE THE NUMBER (
+
2,
-
3).
Group 4 elements do not tend to lose or gain electrons
due to the amount of energy involved so they do not
normally form ionic bonds.

9. ANIONS FROM GROUPS 5, 6 AND 7
Group 15 elements have five valence electrons so
they tend to gain 3 electrons and form 3- ions.
Group 16 elements have six valence electrons so
they tend to gain two electrons and form 2- ions.
Group 17 elements have seven valence electrons
so they tend gain one electron to form 1- ions.
ELECTRONS ARE GAINED OR LOST TO HAVE 8
ELECTRONS IN THEIR OUTER SHELL.

10. TRANSITION ELEMENTS
Transition elements have electron configurations
that allow them to lose different amounts of
electrons from their d-sublevels.
They can form more than one stable ion.
The ions can be distinguished by color.
Here are some common examples:
Lead forms 4+ and 2+
Copper forms 2+ and 1+
Tin forms 4+ and 2+
Hydrogen can form the hydride H
-
as well as H
+
.

11. UNDERSTANDING/KEY IDEA
4.1.D
The ionic bond is due to the
electrostatic attraction between
oppositely charged ions.

12. IONIC CHARACTER
You can predict ionic character by two ways:
Position on the Periodic Table
Electronegativity differences
Position on the Periodic Table
Metals on the left side of the zigzag line tend to lose
electrons.
Non-metals on the right side of the zigzag line tend to gain
electrons.
The highest tendency to form ionic compounds will be
between elements on the bottom left with elements on the
top right.
Electronegativity
Electronegativity values are given in Table 8 of the IB Data
Booklet.
Differences greater than 1.8 are considered to be ionic.

13. UNDERSTANDING/KEY IDEA
4.1.E
Under normal conditions, ionic
compounds are usually solids
with lattice structures.

14. LATTICE STRUCTURE
The ions in ionic compounds surround themselves with
ions of the opposite charge.
Because of this, ionic compounds have three-dimensional
crystalline structures known as ionic lattices.
The strength of force between the ions is known as lattice
enthalpy and depends upon the size of the ion and the
charge on the ion.
The smaller the ion and the greater the charge, the higher
the lattice enthalpy.
The coordination number expresses the number of ions
that surround a given ion in the lattice.
The formula unit is the smallest particle of an ionic
cmpd.

15. APPLICATION/SKILLS
Be able to explain the physical
properties of ionic compounds
(volatility, electrical conductivity
and solubility) in terms of their
structure.

16. PHYSICAL PROPERTIES
Remember physical properties can be observed
without chemically altering the substance.
MELTING AND BOILING POINTS
Ionic compounds have high melting and boiling
points because the electrostatic attraction between
the ions is very strong and requires large amounts
of energy to break the bond.
The higher the charge and smaller the ion, the
greater the melting point.

17. VOLATILITY
Volatility is the tendency of a substance to
vaporize.
Ionic compounds have very low volatility.

18. SOLUBILITY
Solubility is the ease with which the solid dissolves
in a liquid to become a solution.
Solubility trends are based on the similarity of the
chemical nature of the solute and the solvent.
Polar compounds dissolve in polar solvents.
Nonpolar compounds dissolve in nonpolar
solvents
“Like dissolves like”

19. ELECTRICAL CONDUCTIVITY
Electrical conductivity is the ability to conduct
electricity.
Freely moving ions must be present to conduct
electricity.
Molten or dissolved ionic compounds conduct
electricity.
Solid ionic compounds do not because the ions are
locked into place and are not free to move about.

20. BRITTLENESS
Brittleness means the crystal will shatter when
force is applied.
Ionic compounds tend to be brittle because ions of
like charge can be next to each other in the lattice
structure and the repulsive charges cause the
structure to split easily.

21. APPLICATION/SKILLS
Be able to deduce the formula
and name of an ionic compound
from its component ions,
including polyatomic ions.

22. GUIDANCE
Know these polyatomic ions:
NH
4
+
, OH
-
, NO
3
-
, CN
-
HCO
3
-
, CO
3
2-
, SO
4
2-
, PO
4
3-

23. Citations
International Baccalaureate Organization. Chemistry Guide,
First assessment 2016. Updated 2015.
Brown, Catrin, and Mike Ford. Higher Level Chemistry. 2nd ed.
N.p.: Pearson Baccalaureate, 2014. Print.
ISBN 978 1 447 95975 5
eBook 978 1 447 95976 2
Most of the information found in this power point comes
directly from this textbook.
The power point has been made to directly complement the
Higher Level Chemistry textbook by Brown and Ford and is
used for direct instructional purposes only.