CHAPTER 2
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ELEMENTS: Periodic Table
____ total elements : ____ natural and ____ man-made
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ORGANIZATION OF PERIODIC TABLE
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ATOMIC STRUCTURE
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THE NUCLEUS OF AN ATOM
How does an atom stay together?
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ELECTRON ENERGY LEVELS
DIATOMIC ELEMENTS
• Elements that must exist naturally as 2 atoms bonded
together (until it forms a chemical bond with any other
element)
• Br I N Cl H O F
H2
N2
O2
F2
Cl2
Br2
I2
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ISOTOPES
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CHEMICAL BONDING
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Bonding
Sodium is a silver-colored metal that reacts so
violently with water that flames are produced
when sodium gets wet. 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 sodium chloride,
a compound so safe that we eat it every day common table salt!
+
=
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IONIC BOND:
Bohr Method
Bohr Model Method:
Step 1: Draw the energy levels for
each element
Step 2: Show the arrow of transfer.
There should be an arrow showing
transfer for EACH electron given
away. (Just like the top picture)
Step 3: State the ions below each
atomic structure to indicate that
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electrons have been gained or lost.
IONIC BOND:
Lewis Dot Structure
Lewis Dot Method:
Step 1: Write the symbol
for each atom
separately and show
valence electrons
(evenly spread out )
Step 2: No arrows.
Write ions once transfer
has taken place. Show
electrons for the
ORIGINAL outer shell
(the one that gained will
show electrons).
NaCl
MgO
Remember that ions are
written as symbol with
superscript.
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REDOX REACTIONS
Reduction = gain electrons
Oxidation = lose electrons
COVALENT BOND:
Bohr Model
Bohr Model Method:
Step 1: Draw the energy
levels for each element
separately.
Step 2: Show the energy
levels joined (similar to
the top picture)
All diatomic
elements
Demonstrate a
Covalent bond
Remember:
BrINClHOF
(Chlorine is
shown to the
right)
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COVALENT BOND:
Lewis Dot Structure
Step 1: Draw the dot
diagram for each element
individually (use X and •
for different atoms)
Step 2: Draw the dot
diagram for the compound
Step 3: Show the molecular
formula (including lone
electrons)
Molecular formula
Lewis Dot:
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STATES OF MATTER
•
•
•
•
Solid
Definite shape
Definite volume
Tightly packed
Vibrate in place
Liquid
Shape of container
Volume of container
May overlap
Move faster
Gas
No definite shape
No def. volume
Very spread out
Very fast
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CHANGES IN STATE
2 types of Latent
Heat = energy absorbed (stored) or released
Heat of fusion = energy released; Gas to Liquid to
Solid
Heat of Vaporization = energy absorbed; Solid to Liquid to19
Gas
CHEMICAL EQUATIONS
Reactant
Reactant
Reactant
Reactant
Product
Product
Product
Product
Product
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CHEMICAL REACTIONS
Endothermic vs. Exothermic
Exothermic– energy
released – reactants have
more energy than products
Endothermic – energy
absorbed – products have
more energy than reactants
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SECTION 3
WATER AND SOLUTONS
brass
bRONZE
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3
unique
characteristics
of water
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POLARITY
OF
WATER
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HYDROGEN BONDING
(Weak Bond)
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Surface Tension is caused by…
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COHESION / ADHESION / CAPILLARITY
Cohesion attracts molecules of the same kind (water to water)
Adhesion attracts molecules of different kinds (tape and hair)
Capillarity is the attraction of molecules allowing a liquid to rise
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SOLUTIONS
brass
bRONZE
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THE DISSOCIATION OF WATER
Step 1: One water molecule bumps into another water
molecule
Step 2: One of the water molecules dissociates (comes apart).
When water dissociates, hydroxide ions (OH-) and a
hydrogen ion (H+) are produced.
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ACIDS / BASES
Acidity / Alkalinity depends on the amount of hydronium atoms.
HCl + NaOH
NaCl + H2O
(Acid) (Base)---(Salt) (Water)
If hydrogen=
hydroxide =
NEUTRAL
If more hydrogen than
hydroxide = ACID
If more hydroxide than
hydrogen= BASE
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TESTING FOR ACIDS / BASES
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