Name ____________________________________________ Class _____ Date _______________
Chapter 4 – Structure of the Atom
1. Draw a timeline of events representing how the present atomic theory developed.
2. Compare and contrast the atomic theories of Democritus and Dalton. Mark an X under each
name if a statement in the table applies to that person’s theory.
Statement
Democritus Dalton
All matter is made of tiny pieces.
Matter is made of empty space through which atoms move.
Atoms cannot be divided.
Atoms cannot be created.
Atoms cannot be destroyed.
Different atoms combine in whole-number ratios to form compounds.
The properties of atoms vary based on shape, size and movement.
Different kinds of atoms come in different sizes and shapes.
3. Write the name of the persons who proposed the following theories:
________________________
a. Matter could not be divided into smaller and smaller pieces
forever but eventually the smallest possible piece would be
obtained. This piece would be indivisible. He named the
smallest piece of matter “atomos,” meaning “not to be cut.”
________________________
________________________
________________________
________________________
b. All matter is composed of extremely small particles
called atoms
c. Most of an atom consists of electrons moving rapidly
through empty space.
d. All atoms of a given element are identical in size, mass
and chemical properties. Atoms of one element are
different from those atoms of any other element.
e. The electrons are held within the atom by their attraction
to the positively charged nucleus.
4. Matching Type. Match the definition in Column A with the term in Column B. Write the letters
on the blanks provided.
Column A
Column B
____ 1.
A subatomic particle carrying a charge equal to but opposite that of
A.
Atomic number
B.
Gamma ray
C.
Radioactivity
D.
Beta particle
an electron; that is a positive charge of 1+
____ 2.
A particle with two protons and two neutrons with a 2+ charge; they
are emitted during radioactive decay.
____ 3.
A fast-moving electron with a 1- charge; they are emitted during
radioactive decay.
____ 4.
The process by which unstable nuclei lose energy by emitting
radiation in a spontaneous process.
____ 5.
Negatively-charged particles that are part of all forms of matter.
E.
Proton
____ 6.
High-energy radiation that possesses no mass and is not deflected
F.
Alpha particles
by electric or magnetic fields.
____ 7.
The weighted average mass of the isotopes of an element.
G.
Atomic mass
____ 8.
The number of protons in an atom
H.
Electrons
____ 9.
The process in which substances spontaneously emit radiation.
I.
nucleus
J.
Radioactive
____ 10. Ray of radiation emitting from cathode end of a tube used by
researchers to study mass and charge.
____ 11. An equation detailing the atomic number and mass numbers of
decay
K.
Alpha radiation
____ 12. Rays and particles emitted by radioactive materials.
L.
radiation
____ 13. Radiation deflected toward a positively-charge plate in a magnetic
M.
Cathode ray
N.
Mass number
O.
Beta radiation
____ 16. The sum of the number of protons and neutrons in the nucleus.
P.
isotope
____ 17. Radiation deflected toward a negatively-charged plate in a magnetic
Q.
neutron
R.
Nuclear
particles involved in radioactive decay.
field.
____ 14. Tiny, dense, centrally located region within the atom that contains all
of an atom’s positive charge and virtually all of its mass.
____ 15. Atoms with the same number of protons but different numbers of
neutrons.
field.
____ 18. A reaction in which the atom of one element changes into the atom of
another element.
____ 19. A subatomic particle with a mass of nearly equal to that of a proton,
equation
S.
but has no electrical charge.
____ 20. 1/12 the mass of a carbon-12 atom; the standard unit of
measurement for the mass of atoms
Atomic mass
unit (amu)
T.
Nuclear
reaction
5. Organize the properties of subatomic particles by completing the table below.
Electron
Proton
Neutron
Symbol
Location
Relative electrical
charge
Relative Mass (amu)
6. Explain radioactivity by completing the paragraph below.
WORD BANK:
rearranged
identities
affects
electrons
nuclei
nuclear reactions
unstable nuclei
radiation
changes
identities
unstable nuclei
radiation
radioactive decay
different element
In chemical reactions, atoms may be _____________________, but their ________________
do not change. The rearrangement ________________ only the __________________ of the
atoms, not the ___________________. ___________________________ are different. In
nuclear reactions, __________________________ gain stability by emitting ______________.
As a result of ________________________ in the nuclei, the atoms’ ___________________
change. ___________________________ will continue emitting _____________________, in
a process called _______________________________, until stable nuclei, often of a
_____________________________, are formed.
7. Sequence the steps of a nuclear reaction.
___ A stable, nonradioactive atom is formed.
___
Radiation is emitted.
___
The process of radioactive decay continues until the nucleus is stable.
___
An atom has an unstable nucleus.
8. Distinguish between alpha, beta and gamma radiation by completing the table below.
Radiation Type
Alpha
Symbol
Mass (amu)
Charge
Beta
Gamma