Date: October 13, 2015
Aim #15: What role do electrons play in chemical
bonding?
Do Now: Warm-Up Notebook
Date
10/10
Title of Activity
Chemistry Review
Page #
30
HW:
1) Worksheet- Counting Valence Electrons (back)
2) Quiz (Inorganic Chemistry)- Wednesday 10/21
& Thursday 10/22 (day of double period)
What determines an atom’s reactivity?
Electrons
2nd energy level
(8 electrons max)
1st energy level
(2 electrons max)
1st energy level
(2 electrons max)
Usually it is the electrons in the highest energy level
of an atom that determine how that atom reacts
Valence Electrons
The number of electrons present in the highest
energy level.
How many valence electrons
does this atom have?
1
The valence electrons determine
the kinds and number of bonds
atoms can form.
Lewis Dot Structures
Dots are used to represent electrons in the outermost
shell (valence electrons). Dots are placed around the
symbol.
Let’s look at Carbon:
C
Let’s look at Oxygen:
O
Lewis Structures help us determine how many bonds
an atom can form.
Lewis Dot Structure Rules:
1)Determine the number of electrons in the outer
(valence shell).
2) Place a dot at the 12:00 position and continue
in a clockwise direction.
3)Do not form “electron pairs” until you have
completed a circuit.
What are chemical bonds?
Bond
Chemical bonds join atoms
together
Reactions between atoms result in filled outer energy
levels. This makes the atoms stable.
How many bonds can an atom form?
C
O
H
4
2
1
Rule: Atoms can form bonds up to the number of
non-paired electrons in its valence energy level.
Lewis Dot Structures & Bonding
Date: October 14, 2015
Aim #15: What role do electrons play in chemical
bonding?
Do Now: Warm-Up Notebook
Date
10/14
Title of Activity
Page #
31
HW:
1) Worksheet- How will they bond?
2) Textbook Guided Reading 2-2 due Thursday
3) Quiz (Inorganic Chemistry)- Wednesday 10/21 &
Thursday 10/22 (day of double period)
The metals are blue and nonmetals are yellow.
Types of Bonds: Covalent Bonds
Covalent Bond forms when two atoms share
electrons.
**Notice how the energy levels are no longer partially
filled.
Covalent Bonds:
•
Sharing of electrons between two
non-metals
•
In the diagram, two hydrogen atoms
are bonded by a single covalent bond.
The two atoms each share a pair of
electrons.
Review: Number of Bonds an Atom Can Form
• the number of bonds that an atom can form correlates to the number
of electrons that is needed to have a full outer shell
•
•
•
•
H can form 1 covalent bond
O can form 2
N can form 3
C can form 4
Covalent Bonding
Sharing
Double or triple bonds:
•
•
Double Bond- atoms share two pairs of electrons between
them
Triple Bond- atoms share three pairs of electrons between
them
Short hand Method for Drawing Covalent Bonds
• Straight lines can be used to represent a covalent bond between two
atoms.
• A single line is used to represent a single bond
• Two lines are used to represent a double bond
• Three lines represent a triple bond.
• Some single, double, and triple bonds are shown below
Types of Bonds: Ionic Bonds
An ionic bond occurs when an atom transfers an
electron to another atom.
Na loses an electron and becomes a positive ion.
Cl gains an electron and becomes a negative ion.
Activity:
•
Diagram the electron
shell configuration for
Sodium and Chloride
•
What would have to
happen for them to both
have a full outer shell?
•
What Nobel Gas matches
these configurations?
Ionic bonds:
• transfer of electrons between a metal and
a non-metal
• Example: Na+Cl• Metals Lose (e-) and become positive ions
(Cations)
• Nonmetals gain (e-)and become negative ions
(Anions)
• The ions (atom with a charge) in a
compound are attracted to each other due
to opposite charges.
More Ionic Bonds
*
H
*
*
*
*
*
F * *
*
*
Electron
Is transferred
H becomes positive charged (H+)
F becomes negatively charged (F-)
**Notice how the energy levels are no longer partially
filled.
Oxidation & Reduction (REDOX)
Bonding
transfer electrons
share electrons
gain or lose
valence eforming ions
unequal sharing
lose e-
example
Non-metal
negative
(-) ion
examples
example
water (H2O),
HCl
Na+
equal sharing
gain epolar covalent
M etal:
positive
(+) ion
forming
covalent
molecules
between 2
non-metals
Cl-
nonpolar
covalent
examples
O2, N2, Cl2,
F2, Br2
Brain Pop- Chemical Bonds
https://www.brainpop.com/science/matterandchemi
stry/chemicalbonds/