Chemistry of Life
Complete the Table in Your Notes
Protons
Location (within
an Atom)
Charge (neutral,
positive or
negative)
Relative Atomic
Size
(largest,
smallest…?)
Neutrons
Electrons
“Anatomy of an Atom”
Unless told otherwise atoms are neutral.
– What does this tell you about the number of protons,
neutrons and electrons?
Protons = electrons
Number of neutrons can vary (they do not contribute to the
charge)
Nucleus
Consists of Protons and Neutrons held
together by nuclear force.
• Atoms of same type have same number of
protons! (it’s what makes an atom, an atom!)
All oxygen atoms have 8 protons
• Can have different number of neutrons
• Isotopes of the same element
Carbon-12 isotope versus Carbon-14 isotope
--> Carbon-14 has TWO more neutrons
Electrons
•
•
•
•
•
Found in energy levels around the nucleus
They are about 2,000 times smaller than protons or neutrons!
If an atom loses an electron, it will become positively charged.
If an atom gains an electron, it will become negatively charged.
We call these charged atoms ions – an atom that gains or
loses an electron, and has a charge.
Intermolecular forces
• Inter= between (think interstate)
• Attraction between molecules
• Why we have liquid water and it isn’t all gas.
– Forces hold neighboring water molecules together
How does the structure of water contribute
to its unique properties?
Polarity
A molecule in which the charges are unevenly distributed is
said to be polar because the molecule is a bit like a magnet
with two “poles.”
They are written as (-) negative, and (+) positive.
Adhesion
An attraction of Molecules of different substances
Capillary action causes water to rise against gravity
(ex. roots, meniscus reading)
Hydrogen Bonding
• A hydrogen bond is not as strong as a covalent
or ionic bond
• Water molecule attract each other because of
their polarity
• Polarity allows the formation of many hydrogen
bonds that count for many of water’s special
properties
 Cohesion
 Adhesion
 Heat Capacity
Cohesion
An attraction of Molecules of
the same substance
Cohesion causes water
molecule to be drawn
together (beading water
droplets) and causes
surface tension (insects
walking on surface)
Heat Capacity
The large amount of hydrogen bonds causes a large amount of
heat energy to move the molecules and raise the temperature.
Water is said to have a high specific heat
It allows large bodies of water to absorb tremendous amounts
of heat and only cause small temperature changes
Solutions
Waters polarity gives it the ability to dissolve ionic compounds
and other polar molecules. Its is considered the Universal
Solvent because it dissolves so many things.
• Solution: a mixture formed when one substance dissolves another
• Solvent: the substance doing the dissolving
• Solute: the substance being dissolved.
Acid/Base/pH
The concentration of H+ ions on a solution is pH.
Water can be split into H+ and OH- ions.
Acids = a compound that forms H+ ions in the solution
Base = a compound that forms OH- (hydroxide) ions in a solution
Buffer = weak acids or bases that can react with strong acids/bases
to prevent sudden changed in pH
**Buffers dissolved in life’s fluids are important for maintaining
homeostasis in an organism