College Prep Physical Science
Atomic Theory
Name ____________________________________________________
1
Unit Vocabulary
Matter
Element
Atom
Proton
Neutron
Electron
Nucleus
Ion
Scanning tunneling microscope
Earnest Rutherford
Compound
Quarks
Atomic number
Valence electrons
Theory
Law
Inference
John Dalton
Dimitri Mendeleev
Isotope
Hypothesis
Molecule
Atomic Mass
CERN
Unit Objectives
By the end of this unit you should be able to:
 Describe the structure of an atom.
 Compare and contrast the 3 particles that make up an atom based on size, charge and
location.
 Differentiate between an ion and an isotope.
 Determine how scientists know atoms exist without ever having seen them.
 Investigate CERN laboratories and the Big Bang Theory.
 Differentiate between atoms, elements and matter.
 Create a Summary for an adult audience on Particle Physics.
 Calculate atomic and mass number of an atom.
 Differentiate between direct and indirect observations.
 Develop inference skills.
 Synthesize observations into descriptions of atomic mass, number and charge.
 Use a digital interactive animation to create personal definitions
 Calculate atomic number and atomic mass
 Cite examples of the history of Atomic Theory and current experiments
2
“ATOMIC THEORY: How They Discovered Something
Way Too Small to Be Seen”
Excerpt from That’s Not in my Science Book
By: Kate Kelly
Answer each question in the space provided. Be sure to write all answers in your own words. If there are any
questions you find confusing, answer them as best you can and mark them for discussion in class.
1. What is meant by the statement, “…the science of atoms is still in its infancy,”? How long ago was it
determined that atoms exist? (137)
2. Democritus’ came up with the idea of “atomos” (138). What were atomos? What does that word mean?
Did his ideas catch on?
3. How was the scientific definition of the word element different from the Greek definition? (139)
4. Who was John Dalton? What substance sparked his curiosity? (140)
5. How did John Dalton define element? (140)
6. Read the 4 concepts of Dalton’s atomic theory and then list the TWO core concepts of the theory. (141)
a. WRITE THEM IN THE SPACE PROVIDED ON THE NEXT PAGE**
7. What did Ernest Rutherford discover in his gold foil experiment? (142-143)
8. Compare the amount of empty space in an atom to Yankee Stadium (143-144).
3
John Dalton developed the atomic theory using
experimental evidence.
The Atomic Theory states that:
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
Look back at the Scientific Method packet if necessary. Why is this considered a theory and
NOT a law or a hypothesis? Explain.
4
Structure of Matter
Matter is….
Elements are…
Atoms are…
Molecules and Compounds are…
****************************************************************************************
All atoms are made up of 3 particles: protons, neutrons and electrons.
Label them in the diagram and complete the chart.
Charge
Location
Mass
PROTON
NEUTRON
ELECTRON
******************************************************************************************
Carefully observe the results of changes made to atomic structure on the Smart Notebook.
Then describe the following in your own words.
1. Atomic number
2. Mass number
3. Atomic charge
5
Locating Electrons:
- The area around the nucleus where electrons are found is often referred to as the electron
cloud. Since electrons are so tiny and constantly moving, it is virtually impossible to pinpoint
the exact location of an electron. However, the electron cloud contains energy levels and
orbitals and its location can be narrowed down somewhat. Energy levels are regions of the
electron cloud and are often shown as rings around the nucleus; the lowest energy levels are
closest to the nucleus and they get higher in energy as you move further out. Each energy
level contains orbitals, which are regions of space where there is a high chance of locating an
electron.
How many energy levels are shown in the
diagram? ______
How many energy levels have electrons
present? ______
If this atom was neutral overall, how many
protons would it contain in its’ nucleus?
______
Based on the paragraph, describe the terms below:

Electron cloud

Orbital

Energy Level
6
Fill in the table below. A few facts to remember:

The atomic number is the number of _______________.

The mass number is the number of __________________________.

All atoms start out neutral overall (=no charge); that means that the number of _______________
must be equal to the number of ____________________.
Element
Atomic
Number
Potassium
Mass
Number
40
Chlorine
35
Copper
46
70
32
57
59
29
Calcium
20
Silicon
14
Gold
Uranium
18
30
28
Neutrons
19
100
Zinc
Nickel
Electrons
17
Xenon
Bromine
Protons
14
79
200
24
81
98
7
Isotopes
Atoms of the same element can have different numbers of neutrons; the different possible versions of
each element are called isotopes. For example, the most common isotope of hydrogen has no
neutrons at all; there's also a hydrogen isotope called deuterium, with one neutron, and another,
tritium, with two neutrons. An atom is still the same element even if it is missing a neutron or has an
extra neutron. The isotopes of an element, however, have different mass numbers.
Hydrogen
Deuterium
Tritium
**********************************************************************************************************
Ions
The atomic number of an element tells you the number of protons (or positive particles) in an atom.
A normal atom has a neutral charge with equal numbers of positive and negative particles. A normal
atom has a neutral charge with equal numbers of positive and negative particles. That means an
atoms with a neutral charge is one where the number of electrons is equal to the
atomic number.
Atoms, though, can sometimes lose or gain electrons. When an atom loses
electrons, it has a positive charge. When an atom gains electrons, it has a
negative charge. An ion is formed when the atom becomes charged by either
losing or gaining electrons. We will come back to this idea of ions when we begin
bonding.
**********************************************************
1. In the paragraphs above, find the definition of an isotope and an ion and underline/highlight it.
2. How does a neutral atom become an ion?
3. What is different about the isotopes of an element?
8
CHALLENGE: Fill in the table below. Remember, when an atom loses electrons it becomes
________________________ charged; when it gains electrons, it becomes ________________
charged.
Ion
Iodine
Atomic #
-1
Silver+1
Mass #
# Protons
127
26
61
35
Selenium-2
Copper+3
81
16
17
80
79
29
56
56
Sulfur-2
Bromine-1
# Electrons
53
47
Barium+2
Iron+3
# Neutrons
34
35
9
Atomic Theory Review
Answer the following True or False.
T
F
1. Chemistry is the study of matter. It provides answers to the question, “What
is the world made from?”
T
F
2. Atoms can be seen with powerful microscopes.
T
F
3. Protons and neutrons have positive electrical charges.
T
F
4. Atoms are not the smallest units of matter.
T
F
5. An isotope has more protons than electrons.
T
F
6. Neutral atoms always have the same number of protons and electrons.
T
F
7. Ions have the same number of protons and electrons.
T
F
8. Ions have no charge.
T
F
9. The exact location of an electron can be determined.
Self Check Questions: Fill in the Blank.
1. The center of an atom is called the ___________.
2. An atom with more or less electrons than protons is called a ____________.
3. ____________ are atoms that have more or less neutrons than protons.
4. A ____________ is a positively charged particle in the nucleus of atoms.
5. Particles in the nucleus of atoms that have no electrical charge are called ____________.
6. Particles with a negative charge are called _________________.
7. The atomic mass is the combination of ____________ and _______________.
Directions: Connect the person with the proper description.
Rutherford
first to consider the idea of atoms
Dalton
proved that atoms are mostly empty space
Democritus
studying water caused him to consider existence of atoms
10
Changing An Atom
11
Complete the following information… Is the larger number the mass number or atomic number???
element: _Helium________
element: ______Iron________
# protons: ______________
atomic #: ________________
# protons: ______________
# neutrons: _____________
mass #: __________________
# electrons: _______________
Atom or Isotope
Atom or Isotope
element: _____Aluminum_____
Atom or Isotope
element: ____Calcium______
element: ___Neon___________
element: _____Carbon_____
# protons: _______________
atomic #: ________________
# protons: __________
# neutrons: __________
# electrons:______________
# electrons: ___________
atomic weight: __________
atomic weight: ___________
. # neutrons: ____________
Atom or Isotope
Atom or Isotope
element: _____Fluorine______
element: ____Hydrogen_____
element: ______Hydrogen___
atomic #: _______________
atomic #: ________________
# protons: ________________
mass #: ___________
# electrons:_______________
# electrons: _______________
# electrons: ____________
# neutrons: ____________
# neutrons: ____________
Atom or Isotope
Atom or Isotope
Atom or Isotope
Atom or Isotope
12
13