Transcript An atom is the smallest particle of an element that has the chemical

Atoms
This goes in the Chemistry section
of your binder.
An atom is the smallest particle
of an element that has the
chemical properties of that
element.
A single atom is not visible to
the eye. Therefore most
substances are made of millions
or billions of atoms.
The element Hydrogen (H)
#1 on the periodic table,
accounts for 90% of the total
mass of the universe.
Only 1% of the atoms on Earth are
Hydrogen (H) and most of those
are combined with oxygen to form
water, H O
2
Look at the circle graph on page
D 10.
Answer the ?s in your notes.
1. How does the Oxygen (O) on Earth
compare the O in humans?
2. What element is the 2nd highest in
humans? On Earth?
3. Why do you think there is a higher
percentage of (H) in the human body than on
Earth?
4. Humans are mostly composed of what 4
elements?
5. Earth is mostly composed of what 4
elements?
Atoms are made of smaller
particles (sub-atomic);
electrons
protons
neutrons
Match the charge with the
particle:
(+)
(N) neutral
(-)
electron
proton
neutron
A proton is a positively charged
particle.
A neutron is an uncharged
particle.
Where are both particles
located in an atom?
Neutrons and protons have
approximately the same mass.
(+) and (N) are grouped
together in the center of an
atom, called the nucleus.
Electrons are negatively charged
particles that move around the nucleus.
(-) are much smaller than protons, they
are 1/2000 of a proton or neutron. (-)
move around the nucleus of an atom so
quickly their exact positions cannot be
determined. Therefore (-) are
considered a “cloud” around the
nucleus.
Electrons are attracted to the
positively charged protons.
Atoms that have = numbers of
protons and electrons are said
to be neutral.
Go to page D 20
Atoms are identified by their
number of protons. That # is
called the atomic #.
For example: C=Carbon
Atomic # 6
Means 6 protons
Find Chlorine on page D 20
What is the atomic # for Cl?
How many (+)?
The total number of (+) + (N) is
called the atomic mass.
Remember, most of the mass of
an atom is found where?
The number of (+) is = to the #
of (-).
The number of (+) is not always
= to the # of (N).
Look at Carbon again on page
D 20.
The atomic mass is the number
below the element symbol.
What is the atomic mass of C?
When working with atomic
mass, you round off the
number.
(We will tell you what to round to according
to each activity.)
What is the atomic # of O?
What is the atomic mass of O?
How many protons does O
have?
To find the # of neutrons, you
subtract atomic # from atomic
mass.
How many neutrons in O?
Find the atomic #
Find the atomic mass
# of (+)
# of (N)
# of (-)
in the following elements
1. Ne 2. N
3. Li 4. K
5. Au 6. Hg 7. Sn 8. S
9. Cl 10. Ca