Atoms and Elements
Chapter 6: The Chemistry of Life
Atoms are the
basic units of
all matter.
Atoms are
composed of 3
sub-atomic
particles:
1. Protons (+)
2. Neutrons (0)
3. Electrons (-)
Elements
An atom is the
smallest particle
of an element.
An element is a substance that can
not be broken down into simpler
chemical substances.
Everything is made of substances
called elements.
Each element is identified by a oneor two-letter abbreviation called a
symbol.
Atomic number
The atomic number is
equal to the number of
protons that an atom has.
Ex. Silver has an atomic
number of 47 and
therefore has 47 protons
Atoms always contain the
same number of protons and
electrons
Atomic # = protons = electrons
Atomic Mass
The atomic mass is the number of protons
and neutrons added together.
How do you figure how many neutrons
there are?
Atomic mass - atomic number = number of neutrons!
The Fab Five Elements
In Biology this year, we will be focusing on
5 main elements.
They are…
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Notice just how much of the human
body they compose
That’s 96.8% of your total body composition!
Carbon
Atomic Number: 6
• Atomic Mass: 12.01
• Carbon is the basis for organic
organisms as it occurs in all living
things.
• Makes up about 18% of human bodies
• Examples: found in carbohydrates,
lipids, proteins and nucleic acids
•
Carbon in Chemical
Structures
Carbons are
Carbon is so common
in living organisms
that they can
sometimes be
omitted to save time.
Anywhere there is a
corner without a letter,
that means a carbon is
actually there.
represented
By the letter
C
Hydrogen
• Atomic
Number: 1
• Atomic Mass: 1.01
• Hydrogen is the most abundant
element in the universe
• Makes up about 10% of human
bodies
• Examples: found in carbohydrates,
lipids, proteins and nucleic acids
Hydrogen in Chemical
Structures
Hydrogen is
represented
By the letter
H
Oxygen
 Atomic Number: 8
 Atomic Mass: 15.99
 Animals and plants require Oxygen
for respiration
 Makes up about 65% of human
bodies
 Examples: found in carbohydrates,
lipids, proteins and nucleic acids
Oxygen in Chemical
Structures
Oxygen is
represented
By the letter
O
Nitrogen
 Atomic Number: 7
 Atomic Mass: 14.01
 Nitrogen gas (N2) makes up
78.1% of the volume of the
Earth's air.
 Makes up about 3% of human
bodies
 Examples: found in proteins and
nucleic acids
Nitrogen in Chemical
Structures
Nitrogen is
represented
By the letter
N
Phosphorus
 Atomic Number: 15
 Atomic Mass: 30.97
 Important for proper
skeletal and nervous
system function
 Makes up about 1% of
human bodies
 Examples: found in nucleic
acids
Phosphorus in Chemical
Structures
Phosphorus
is
represented
By the letter
P
Directions: Label each of the Fab Five
Elements in the chemical compound
(Adenosine Triphosphate a.k.a ATP)
below.
Directions: Label each of the Fab Five
Elements in the chemical compound
(glucose) below.