NAME:_______________________
1.3 How does an ion form and why?
DATE:____________
AHS Instructor Ms. Kasia Room 109/110
UNIT 1 CHEMICAL BONDING: IONIC
1.4 How does Ionic Bonding Work?
AIM:
DO NOW: Draw the Lewis Structure for Calcium
How many electrons does Calcium want to gain ___________ or lose _____________
?
Write the ion that is formed (don’t forget the charge!).
Why does an ion have a charge?
Does the radius of this Calcium ion increase of decrease?
THINK MODELS
Directions: Fill in the blanks to help you use this analogy to understand ions
_______________ MODEL is a
______________________ thing
in the fashion industry
_______________ MODEL is a
________________ thing in the
fashion industry
REVIEW: HOW DOES AN ION FORM?
Lewis Dot Diagram
Gain:_____________
Lose:_____________
BOND. CHEMICAL BOND
What is your definition of a bond?
Ion:
Charge:
BOND. CHEMICAL BOND
CHEMICAL BOND:
Directions: Complete 1.4 Reading and 1.4 Activity Worksheet to define the following new vocabulary.
Your Definitions:
IONIC BOND:
CHEMICAL BOND:
TYPES OF CHEMICAL BONDS (class definitions)
IONIC BOND
COVALENT BOND
HOW DO WE BOND ATOMS?
CRISS-CROSS RULE
LET’S TRY SOME
MgF2
Lewis Dot
Diagram
Transfer e-
Ions Formed
Chemical
Formula
CH4
NAME:___________________
1.4 Independent Practice
DATE:________________
AHS Instructor Ms. Kasia Room 109
UNIT 1 CHEMICAL BONDING: IONIC
1.4 Independent Practice
Directions: Complete the Independent Practice and hand it in at the end of the period.
1. Identify whether the bonds are ionic or covalent. Indicate how you arrived at your answer.
Explain how you arrived at your answer
MgCl2
Explain how you arrived at your answer
CH4
Explain how you arrived at your answer
Cl2
2. For the following atoms (1) draw the Lewis Dot Diagram, (2) write down the ions that they would
become if they gained/lost electrons, (3) show the transfer of electrons between the atoms. Last, write
the chemical formula of ionic compounds that are formed.
EXAMPLE 1
a. LEWIS DOT DIAGRAM:
K
Cl
Na
O
b. IONS FORMED:
c. SHOW TRANSFER OF
ELECTRONS BETWEEN
THE ATOMS:
d. CHEMICAL FORMULA:
EXAMPLE 2
e. LEWIS DOT DIAGRAM:
f. IONS FORMED:
g. SHOW TRANSFER OF
ELECTRONS BETWEEN
THE ATOMS:
h. CHEMICAL FORMULA:
EXTRA CREDIT!
Conduct the following reading. Use the following symbols to track your reading:
I understand
This is important
? I am confused
! This is interesting
INDEPENDENT READING
In 1916, the American chemist Gilbert Newton Lewis proposed that chemical bonds are formed
between atoms because electrons from the atoms interact with each other. Lewis had observed that
many elements are most stable when they contain eight electrons in their valence shell. He
suggested that atoms with fewer than eight valence shells bond together to share electrons and
complete their valence shells.
While some of Lewis' predictions have since been proven incorrect (he suggested that electrons
occupy cube-shaped orbitals), his work established the basis of what is known today about chemical
bonding. We now know that there are two main types of chemical bonding; ionic bonding and covalent
bonding.
IONIC BONDING
Let's look at an example. The element sodium is a silver-colored metal that reacts so violently with
water that flames are produced when sodium gets wet. The element chlorine is a greenish-colored gas
that is so poisonous that it was used as a weapon in World War I. When chemically bonded together,
these two dangerous substances form the compound sodium chloride, a compound so safe that we eat
it every day - common table salt!
enlarge image
Notice that when sodium loses its one valence electron it gets smaller in size, while chlorine grows larger
when it gains an additional valence electron. This is typical of the relative sizes of ions to atoms. Positive
ions tend to be smaller than their parent atoms while negative ions tend to be larger than their parent.
After the reaction takes place, the charged Na+ and Cl- ions are held together by electrostatic forces,
thus forming an ionic bond.
The fact that ionic compounds are solids, results from the intermolecular forces (forces between
molecules) in ionic solids. If we consider a solid crystal of sodium chloride, the solid is made up of
many positively charged sodium ions (pictured below as small gray spheres) and an equal number of
negatively charged chlorine ions (green spheres). Due to the interaction of the charged ions, the
sodium and chlorine ions are arranged in an alternating fashion as demonstrated in the schematic.
Each sodium ion is attracted equally to all of its neighboring chlorine ions, and likewise for the chlorine
to sodium attraction. The concept of a single molecule does not apply to ionic crystals because the solid
exists as one continuous system. Ionic solids form crystals with high melting points because of the
strong forces between neighboring ions.
Sodium Chloride Crystal
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
Cl-1
Na+1
NaCl Crystal Schematic
COVALENT BONDING
Because both of the nonmetals will want to gain electrons, the elements involved will share electrons in
an effort to fill their valence shells. A good example of acovalent bond is that which occurs between
two hydrogen atoms. Atoms of hydrogen (H) have one valence electron in their first electron shell.
Since the capacity of this shell is two electrons, each hydrogen atom will "want" to pick up a second
electron. In an effort to pick up a second electron, hydrogen atoms will react with nearby hydrogen (H)
atoms to form the compound H2. Because the hydrogen compound is a combination of equally matched
atoms, the atoms will share each other's single electron, forming one covalent bond. In this way, both
atoms share the stability of a full valence shell.