What is
the world
made of,
and how
is it all
held
together?
Nothing…
…if the earth is
the nucleus of
an atom, the
electrons are
twice as far
away as pluto
CB 2.4
Atoms are made of:
protons neutrons electrons
CB 2.8
Each element is defined by the
number of protons, has an equal
number of electrons, the number
of neutrons may vary.
The Periodic Table
of the Elements
Atoms can be combined together to
make molecules
How do atoms form molecules?
An atom’s chemical characteristics are
determined by the number of electrons it has.
Bonds holding atoms together:
• Covalent
– Strong
– Sharing Electrons
– When broken =
chemical reaction
• energy consumed or
released
• Ionic
– Weak
– Positive and Negative
atoms attracted to each
other
CB 2.13
Ionic bonds- electrons donated/accepted then
atoms attracted by opposite charge
CB 3.6
Ionic bonds are
easily broken
Bonds holding atoms together:
• Covalent
– Strong
– Sharing Electrons
– When broken =
chemical reaction
• energy consumed or
released
• Ionic
– Weak
– Positive and Negative
atoms attracted to each
other
CB 2.11
Covalent bondsatoms share
electrons
CB 8.14
a chemical reaction makes or breaks
covalent bonds
Electron sharing in a covalent bond is not
CB 2.12
always equal
water
+
+
CB 2.12
polar versus non-polar molecules
+
H
+
+
+
water
H
H
C
+
+
H
methane
Bonds holding atoms together:
• Covalent
– Strong
– Sharing Electrons
– When broken =
chemical reaction
• energy consumed or
released
• Ionic
– Weak
– Positive and Negative
atoms attracted to each
other
Four types of molecules that are
primarily found in living systems
(biomolecules):
•Carbohydrates/ Sugars
•Nucleotides- DNA/RNA
•Amino Acids- Proteins
•Lipids- fats/phospholipids
Videos:
http://www.microscopyu.com/moviegaller
y/livecellimaging/a549/index.html
http://sunflower.bio.indiana.edu/~rhangart/
plantmotion/starthere.html
CB 6.2