NAME ________________________________________ CLASS ________ DATE __________
4.1 Defining the Atom
1.
2.
How is the gift inside a wrapped present like the atom? ___________________________
Define atom _____________________________________________________________
________________________________________________________________________
3. John Dalton is considered the “father” of atomic theory. Why does he have this honor
rather than Democritus, who first proposed the concept of the atom?
_______________________________________________________________________
4.
Dalton’s atomic theory
proposed that: (note: during this chapter, you will find out that
Dalton made 2 mistakes. Correct them here, when you figure out what they are.)
a) All elements are composed of tiny indivisible particles called _________________.
b) Atoms of the same element are identical, but different from __________________
___________________________________________________________________
c) “Atoms of different elements can ______________________ mix together or
______________________ combine in simple whole-number ratios.”
d) Chemical reactions occur when atoms are rearranged. In a chemical reaction,
atoms of one element can NEVER
change into a different element.
Note: There is a type of reaction
in which atoms of a one element
can turn into atoms of a different
element. Do you know what type
of reaction it is?
SOMETIMES ALWAYS

5. Atoms are incredibly tiny; however, scientists can observe individual atoms using a
____________________ ____________________ microscope. The ability to “see”
(and act!) on such a small scale is leading to the amazing new field called nanotechnology . Give 4 examples of future applications it could be essential to.
a) _____________________________ b) ____________________________
c) _____________________________ d) ____________________________
4.2 Structure of the Nuclear Atom
1. How do doctors “see” your bones without cutting you open? _______________________
2.
Dalton’s model of the atom was a giant step forward; however, he didn’t get everything
right; there are two things about which he was proved wrong. The first error was
discovered by a scientist named J. J. Thomson.
Thomson discovered the ___________________________, the first known
______________________________ particle. This meant that atoms are actually
INDIVISIBLE DIVISIBLE. The technology he utilized to do this was a
_________________________ ________________ tube.
3. The symbol for the electron is _____________
Fill in the blank spaces on the chart below about the three major subatomic particles.
4. J.J. Thomson developed a model of the atom called the __________________________
_____________________________ model. The “raisins” were ___________________

5.
To test Thomson’s model of the atom, Ernest
Rutherford performed a very important experiment called the Gold Foil Experiment.
Answer the following questions about this experiment. a. What were the particles he shot at the gold foil? ______________________________
These particles have a POSITIVE NEGATIVE NEUTRAL charge. b. Based on the Plum Pudding model, he expected that the particles would be
UNDEFLECTED SLIGHTLY DEFLECTED GREATLY DEFLECTED
by the gold foil. c. Most of the particles went straight through the _______________________,
completely unaffected! To explain this, Rutherford proposed a new model of
the atom. He said that almost all of the particles went straight through because atoms
are mostly ___________________________ space. d. He was also completely astonished when a few of the particles bounced back. To
explain this, Rutherford proposed the existence of a region at the center of the atom
that he named the ____________________________. The mass of this region must
include NONE SOME ALMOST ALL of the mass of the atom. He knew that
the charge of this region must be POSITIVE NEGATIVE NEUTRAL. How
did he know this? _____________________________________________________
What new technology did Rutherford use in his experiment? Hint: Radioactivity was a
relatively new concept at the time. http://reich-chemistry.wikispaces.com/file/view/atom_pic.gif/147085355/atom_pic.gif
6. Rutherford’s model of the atom was
likened to a little solar system.
In his model the sun is the
_____________________________
and the planets are the
_____________________________

4.3 Distinguishing Among Atoms
1. All atoms have ______________________ and ______________________ that make
up the nucleus, and ______________________ that are somewhere in the empty space.
The thing that makes one element different from another element is the number of
____________________________. This is called the atomic number of the element.
** This is the only factor that determines which element an atom is.
**
2. To be neutral, the number of negatively charged particles must be __________________
to the number of positively charged particles.
3. Assuming that an atom is neutral (i.e., it has no charge), how can you determine the
number of electrons that atom has? ________________________________________
Carefully study Sample Problem 4.1. Then do problems 16 and 17. Assume that all of
the atoms are neutral. Note: The answers to these problems are in the back of your
book, in Appendix E.
SHOW YOUR WORK HERE
For some of the problems in this chapter, you may need to use Table 4.2 in your book
OR there is another table you could use that a chemist is never without. Do you know
what it is? How would it help you in the chapter 4 problems?

4.
5.
Define mass number . _____________________________________________________
If you know what element an atom is, and you know its mass number, how can you
determine the number of neutrons that atom has? ________________________________
_______________________________________________________________________
6.
“The composition of any atom can be represented in _____________________________
______________________________ using the atomic number and mass number as in
Figure 4.8.”
7. In this notation, the _________________ number is the subscript. The ______________
number is the superscript.
8. Carefully study Sample Problem 4.2. Then do problems 18 and 19. Assume that all of
the atoms are neutral. Reminder: The answers to these problems are in the back of
your book, in Appendix E.
SHOW YOUR WORK HERE
9. Back in section 4.2 (#2), we said that Dalton got 2 things wrong. The first was that atoms
are actually divisible.
What was the second thing? ______________________________
_______________________________________________________________________
10. Define an isotope _________________________________________________________
_______________________________________________________________________
11. Two of the main isotopes of carbon are carbon-12 and carbon-14. What is the actual
physical difference between these two isotopes? ______________________________
______________________________________________________________________
Note: The chemical behavior of different isotopes of the same element is identical.

You may ask – if different isotopes of the
same element behave the same in chemical
reactions - then why should isotopes matter?
Have you heard of carbon-14 before? There
is a VERY big difference between carbon-12
and carbon-14; do you know what it is?
12. Carefully study Sample Problem 4.3. Then do problems 20 and 21. Reminder: The
answers to these problems are in the back of your book, in Appendix E.
SHOW YOUR WORK HERE
13. What is an atomic mass unit (amu) ? _________________________________________
________________________________________________________________________
14.
Amu’s are a unit of mass – just like grams. Why don’t we use grams instead? ________
________________________________________________________________________
16. Define atomic mass _______________________________________________________
________________________________________________________________________
17. On p. 116 , answer the questions on the Interpret Data.
a. Identify ______________________________________________________________
b. Describe ______________________________________________________________
________________________________________________________________________
In this chapter, you have read about 3 important numbers: atomic mass, mass number,
and atomic mass. Two of these are on the periodic table, and one is not. Which ones
are on it, and which one is not?
Why?!