The Atom
Consider Russian nesting dolls. Each
one is smaller than the one before it.
If each doll is ½ the height of the one
before it, how many would it take to
make a stack 4 feet tall? The first doll
is 2 feet tall.
• Now consider a block of wood.
• How many times can you divide a
block of wood in half?
• What do you get each time?
• What do you have at the end?
• At some point, you cannot divide that
block any more without changing its
properties as wood.
–You cannot divide the molecule
without breaking it into its atoms.
Atoms
• Atoms are the fundamental building blocks of
all matter.
• Atoms have distinct properties and combine
with each other based on these.
• These properties come from each atom’s
makeup of PROTONS, NEUTRONS, and
ELECTRONS.
“Just how small is an atom?”
• TED talks!
• https://www.ted.com/talks/just_
how_small_is_an_atom
• Full of great informational,
entertaining videos – check it
out!
Protons
• Each atom contains a set number of PROTONS.
• Protons carry a positive charge (+1).
• Each proton has a mass – a very small mass.
– A mass so small we measure it in atomic mass
units (amu).
– Protons have a mass of 1 amu.
• As a side note, the number of PROTONS in the
nucleus is the ONLY thing that decides what
kind of atom you’re looking at.
– 6 protons, 8 neutrons
– 8 protons
– 12 electrons
• AHA! Sometimes this doesn’t work!
Neutrons
• NEUTRONS, along with protons, are found in
the atom’s core – the nucleus.
• Neutrons have a neutral charge (no charge).
• Neutrons are just as heavy as protons.
– They have a mass of 1 amu.
The Nucleus
• The NUCLEUS is the solid core of every atom,
and contains essentially ALL of the atom’s
mass.
• Atomic mass = # protons + # neutrons
• Find the weight of each nucleus in atomic
mass units (amu).
# Protons
6
12
5
23
47
15
17
# Neutrons Atomic Mass Element
7
C
15
Mg
9
B
41
V
59
32
61
Cu
39
P
83
109
51
Electrons
• ELECTRONS are the negativelycharged particle of the atom
• They have a charge of -1
• BUT! They have very little mass.
• We consider this mass to be 0 amu.
• Electrons are found in a “cloud”
around the atom.
The Cloud
The Cloud (cont’d)
• BUT! Electrons have distinct energy levels
within that cloud.
• We won’t worry about this just yet, but know
that there is some order to the way these
electrons are organized.
• In neutral atoms, there are equal numbers of
protons and electrons.
– Why is this?
• Hint: Neutral atoms have 0 total charge.
– What would a formula for total charge look
like?
# Protons # Electrons Total Charge
12
0
56
0
24
+1
109
-1
38
+2
• Atoms interact with each other to form bonds.
– Electrons do all the interacting.
• Of all the electrons, only those in the highest
energy levels participate in bonding. We’ll talk
more on this later.
• There are 3 different kinds of bonds
– Ionic bonds
– Covalent bonds
– Metallic bonds
• Bonds hold atoms together to form ELEMENTS
and COMPOUNDS.
Elements
• Compounds which are made up of only one
type of atom are called ELEMENTS.
• Atoms have the properties of their element.
• What are some examples of elements?
• Pure metals use metallic bonds to share
electrons.
Molecules
• A MOLECULE is a combination of 2 or
more chemically-bonded atoms.
• Molecules may be made up of
several kinds of atoms.
–Or, they may be the same, like O2
(oxygen gas)
Compounds
• COMPOUNDS are substances that are formed
when two or more different elements bond.
• Compounds can display ionic or covalent
bonds.
– Ionic bonds come from an unequal sharing of the
electrons.
– Covalent bonds come from an equal sharing of the
electrons.
Practice
Compound, element, or molecule?
• H2O
• Baking soda (NaHCO3)
• Copper
• Gold
• HCl
• CO2
• Starch
• Molecules have entirely different
properties than those of the
parent atoms.
–Molecules may look and act
completely different than the
elements that make it up.
• An example, you ask? Alrighty
then….
Sodium is a highly reactive metal. So much so,
that it needs to be kept in oil, because it would
react with oxygen and water in the air
otherwise.
Chlorine gas is used as a chemical weapon in
some places. It is highly toxic (although, people
who described its scent generally described it
somewhere between pepper and pineapples).
• http://www.cbsnews.com/news/syriapurportedly-using-chlorine-gas-attacksagainst-civilians-video-shows/
How many of you think the
cafeteria food here is always
perfect just the way it is?
What would you do if you wanted to
flavor it?
…Yep. Salt.
Which element is it?
1. Grab an egg.
2. Open the egg.
3. DO NOT EAT THE CANDY YET!
4. Determine the element.
5. ????
6. Profit!
Fill in the chart
Element
# Protons # Neutrons # Electrons Mass # Atomic #
Hydrogen
Carbon
1
1
6
7
4
20
11
12
14
9
23
9
7
4
10
23