Ch. 4.1 - 4.2
Objectives
1. List the most common elements in living
things
2. Compare & contrast elements and
compounds
What is Matter?
• Matter:
– anything that occupies space and has mass
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Atoms
• Atom:
– the smallest possible particle of an element
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One hundred millionth of an inch in diameter
A piece of paper is 1 million atoms thick
Atomos: greek word meeing ‘indivisible’
How small? 3 million carbon atoms to cover a “.”
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What do atoms consist of?
• Subatomic particles
– Protons: positive (+)
• # of protons = atomic number
– Electron: negative (-)
• Very little mass
– Neutron: neutral
• Usually equal to or slightly
greater than # of protons
• An element’s properties
depend on arrangement of
subatomic particles
More interesting atom facts…
• There are more atoms in your hand than all
the grains of sand in all the beaches in the
world
• There are more atoms in a milliliter of water
than drops of water in all the lakes and
rivers in the world
Where are the protons, neutrons
and electrons located?
• Nucleus:
– central core
– containing protons and
neutrons
– Occupies only a trillionth of
an atom’s volume, but has the
most mass
• Electrons move about
OUTSIDE of nucleus
• What keeps the electrons
from flying away?
• The (-) (+) attraction with
the protons
A bit more about electrons . . .
• Most models represent
electrons as a “cloud.”
Why?
• Exact path of electron can
NOT be determined
• Model NOT to scale.
– i.e., baseball stadium/fly
• A proton and a neutron
weigh about 1,860 times
more than an electron
Elements
What do you know about these
elements?
Interesting Facts:
• Nitrogen: makes up 78% of earth’s
atmosphere
• Oxygen: makes up 20% of earth’s
atmoshphere
• Carbon is a solid comprising materials such
as coal, graphite, and diamonds
• Hydrogen: comprises 70% of the sun
Elements and the Greeks
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What are elements?
• Elements:
– pure substances that can NOT be broken down into other
substances by chemical means
• The basic ingredients of matter
Modern Elements
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Elements vs. Trace Elements
• Trace elements:
– Less than 0.01% of body
but critical to your health
• i.e, need .15mg of iodine
or thyroid won’t function
properly
• i.e., iron, 0.004% of body,
essential for carrying
oxygen in your blood
• What are the four most
abundant elements in
your body (in order)?
What are Compounds?
• Compounds:
– substance containing two or more elements that
are chemically combined in a fixed ratio
Yummy
dangerous
dangerous
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