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Transcript
The Atom
Consider Russian nesting dolls (matryoshka
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 3
feet tall?
How many times can you divide a block of wood
in half? What do you get each time? At the
“end?”
• At some point, you cannot divide that
block any more without changing its
properties as wood.
• Even further on, 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.
Protons
• Each atom contains a set number of protons.
• Protons carry a positive charge
• 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. We
measure their mass in atomic mass units
(amu).
– 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.
Electrons
• Electrons are the negatively-charged 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.
• 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.
• Examples of these would be copper (Cu),
aluminum (Al), silver (Ag), hydrogen (H), etc.
• Pure metals use metallic bonds to share
electrons.
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.
Molecules
• Molecules may be made up of several kinds of
atoms.
• A MOLECULE is the smallest unit that
maintains the properties of a compound.
• Molecules have entirely different properties
than those of the parent atoms.
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).
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.
Practice
Compound, element, or molecule?
• H2O
• Baking soda (NaHCO3)
• Copper
• Gold
• HCl
• CO2
• Starch
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