KEY
Name: __________________________ Hour: _____________
Atom Notes
Let’s review!
What makes up everything we can touch and feel? The whole universe? _______MATTER__________
Matter is made of particles. When we heat something up, what happens to the particles?
The particles move faster and farther apart.
When we cool something down, what happens to the particles?
The particles move slower and closer together.
Remember the food coloring in the water? The food coloring spreads faster in the hot water because the
molecules are moving faster. Although the particles in the water are too small to see, we can still see the
effect of their movement by the spreading of the food coloring. The faster the particles move, the faster
food coloring spreads.
So what are these particles that all matter is made of? These particles are called ___ATOMS________.
When two or more atoms combine together they form a___________________MOLECULE_________.
Atoms are the smallest particle into which an element can be divided and still be considered the
same substance.
How big are atoms?
1. Let’s do a demonstration with salt. How big are atoms?
The average sized grain of salt has 1.2 x 1018 atoms.
2. Now let’s look at the piece of aluminum foil given to you by the teacher. What is the smallest particle of
matter within the piece aluminum? How small is each of the
___________ within the aluminum foil? Aluminum atoms are average sized atoms and are
.00000003 cm. (3 hundred millionths of a cm).
How many aluminum atoms stacked together would it take to equal the thickness of a piece of aluminum
foil. 50,000 aluminum atoms thick.
3. Now take a look at the penny that was given to your group. The penny contains about how many
atoms? 20,000,000,000,000,000,000,000 which is 20 thousand billion billion.
Please open your book to page 87. Please look at figure 10 and describe in a few sentences how small
an atom is using the figure 10 as a helper.
The size of atoms varies. Helium has the smallest diameter. About 600 Helium atoms would fit
in the space occupied by one Francium atom.
Wow! That’s small. How did people discover atoms? Let’s go back in time and find out!
Discovery of Atoms:
Democritus
One of the scientists to challenge the big question of matter, 2000 years ago.
1. What did Democritus discover? Matter can’t be divided into
smaller and smaller pieces forever Eventually, the smallest
piece will be obtained.
2. What did he name? The atom. From the Greek word
“atomos” which means indivisible.
Dalton
In 1803, John Dalton proposed the Atomic Theory. He performed a number of experiments that helped
him develop this theory. There are 4 parts to his Atomic Theory:
1. All elements are composed of atoms
2.
Atoms of the same element are exactly the same
3. Atoms of different elements are different
4. Molecules are formed by joining two or more atoms together.
Thomson
In 1897, Thomson was studying what happened when he passed an electric current through a gas. The
gas gave off negatively charged particles even though the gas was uncharged (neutral). Where did they
come from?
1. What did Thomson discover?
Electrons
2. What did Thomson’s model of the atom look like? We call it the chocolate chip cookie model.
You'll come closest to Thomson's picture if you think of the ball of dough on the cookie
sheet before it's baked--that is, if you think of the atom as a sphere rather than the
usual flat shape of a cookie
Rutherford
In 1908, Ernest Rutherford was experimenting with shooting a stream of tiny positively charged particles
at a sheet of very thin gold foil. Most went straight through and some bounced off to the side or right back
at him as if they had hit something solid. Let’s draw a picture of his experiment:
A beam of positively charged
particles through a piece of gold
foil. Some particles deflected
but most passed straight
through.
1. What did Rutherford discover?
Atoms are mostly empty space. Atoms have a positively charged center called a nucleus.
He basically proved that the atom had a nucleus with protons.
2. What did Rutherford’s model of the atom look like?
Bohr
In 1913, Niels Bohr proposed his “Planetary Model” of the atom. In this model, the electrons orbit around
the nucleus in different energy levels, similar to how planets orbit around the Sun.
1. What did Bohr’s model of the atom look like?
This is what we know about atoms:
1. The center of the atom is called the nucleus. It contains protons (+) and neutrons (no charge).
2. Orbiting around the outside of the nucleus are teeny, tiny electrons (-).
3. In order for an atom to remain neutral, the number of ______ protons _________ must equal the
number of _____ electrons ___________________.
4. Most of the atom is made of ________________empty space__________________________.
What’s inside and Atom? :
For this section, please open your blue Matter text to page 88 and read pages 88-89 and answer the
following questions.
1. What smaller particles form the nucleus of the atom? Is the nucleus of an atom the same as a nucleus
of a cell? Explain Why or Why not.
Protons and neutrons form the nucleus of the atom. No it is not the same as the nucleus of the
cell because it doesn’t control the activities of the atom such as a nucleus of the cell. It is called
the nucleus to represent the center of the atom. It is also not considered living. Therefore there
are no “life” functions that need to be carried out by the nucleus of an atom.
2. Explain why atoms are neutral in charge.
Atoms are neutral because the number of protons and the number of electrons are the same.
Thus, the positive charges and negative charges cancel out.
3. Why do scientists say that most of the mass of an atom is located in the nucleus?
Protons and neutrons are located in the nucleus, and electrons outside the nucleus. Because an
electron has almost zero mass and a proton and a neutron have a mass of 1 atomic mass unit
each, most of the mass of an atom is in the nucleus.
4. Draw a current model of the atom. Electrons travel in clouds around the nucleus in different
orbits.
Let’s fill in the following chart
Atomic particle
Location
Charge
PROTON
INSIDE
Positive (+)
ELECTRON
Outside the nucleus
NEGATIVE (-)
Neutron
INSIDE
NEUTRAL
5. Now that you know about how atoms relate to matter and how the parts of an atom relate to an atom,
on a separate sheet of paper please use the following words below to design your own concept map.
Your concept map must include all of the words and clues that are 1-2 sentences used to connect each of
the words (concepts) of your map.
Words: Atom, Molecule, Compound, Property, Matter, Electron, Nucleus, Neutron, Proton, solid, liquid,
gas, phases of matter, structure, density, mass, volume, state, conductivity, solubility, malleability.
6. Now that you are all finished please get a laptop computer and explore the websites listed below in
order. Be sure to explore each one very carefully. You may need to remember info from each of the sites.
Model of an Atom:
http://www.windows.ucar.edu/tour/link=/sun/Solar_interior/Sun_lay...
All about Atoms:
http://education.jlab.org/atomtour/index.html
The Atom’s Family
http://www.miamisci.org/af/sln/credits/index.html