Name: ____________________________________________
Class: ___________
Support activities – Second year of Secondary Cycle Two
ACTIVITY 1
ANSWER KEY
Date: __________________
ST
TEXTBOOK: Chapter 1, pages 6–15
RELATED HANDOUT: Concept review 1
The atom and atomic models
1. Complete the following sentences, using the words or groups of words in the box below. You
may not need some words, and you may use others more than once.
• alpha
• Dalton
• neutral
• Rutherford
• Aristotle
• Democritus
• neutrons
• Rutherford-Bohr
• beta
• different
• orbits
• sheet of gold foil
• billiard ball
• electron(s)
• plum pudding
• simplified atomic model
• Bohr
• gamma
• positive
• Thomson
• Chadwick
• identical
• protons
• compounds
• negative charge
• radioactivity
a) In Ancient Greece, two great philosophers had opposing ideas about the nature of matter.
Aristotle
Democritus
__________________
believed that matter was infinitely divisible. ___________________
,
on the other hand, maintained that matter was made up of tiny indivisible particles.
Dalton
b) In the 19th century, ____________________
created an atomic model in which atoms
billiard balls
resemble ____________________
. His theory was in line with Democritus’ idea. Dalton
added four important points:
identical
– All the atoms of an element are ____________________
.
solely for classroom use with Observatory.
© ERPI Reproduction and adaptation permitted
– Matter is composed of atoms (indivisible particles).
different
– The atoms of different elements are ____________________
.
– In chemical reactions, atoms combine in specific proportions to form different
compounds
____________________
.
Thomson
c) Another researcher, ____________________
, worked with cathode ray tubes. He
electron
negative charge
discovered the ____________________, a particle with a ____________________
.
This discovery led him to modify Dalton’s atomic model. Thomson’s model resembles a
positive
plum pudding
____________________
: the atoms are like a ____________________
dough, and
the fruit represents the negative particles.
Observatory / Guide
11129-B
1
ANSWER KEY
Support activities – Second year of Secondary Cycle Two
ACTIVITY 1
The atom and atomic models
Name: ____________________________________________
Class: ___________
Date: __________________
d) At the beginning of the 20th century, the field of science made great strides thanks to the
radioactivity
study of ____________________
. The discovery of three types of radiation led to further
alpha
evolution of the atomic model. The three types of radiation are ____________________
beta
particles, which are positively charged, ____________________
particles, which are
gamma
negatively charged, and ____________________
rays, which are electrically neutral.
Rutherford
____________________
wondered about the position of electrons in the atom. He decided
sheet of gold foil
to bombard a fine ____________________
with a stream of alpha particles. He obtained
the following results: the atom is mainly composed of empty space but contains a small,
dense and positive nucleus. In his atomic model, the nucleus is composed of positively
protons
charged particles called “____________________
,” and negatively charged particles called
electrons
“____________________
” circle the nucleus.
Bohr
e) Rutherford’s atomic model was improved by ____________________
, who showed that
electrons do not move around the nucleus randomly; they follow specific pathways that
orbits
Bohr described as “____________________.
” This is clearly illustrated by the
Rutherford-Bohr
____________________
atomic model.
2.
Draw an oxygen atom according to each of the following atomic models.
b) Thomson’s atomic model
solely for classroom use with Observatory.
© ERPI Reproduction and adaptation permitted
a) Dalton’s atomic model
Observatory / Guide
11129-B
2
ANSWER KEY
Support activities – Second year of Secondary Cycle Two
ACTIVITY 1
The atom and atomic models
Name: ____________________________________________
Date: __________________
d) the Rutherford-Bohr atomic model
solely for classroom use with Observatory.
© ERPI Reproduction and adaptation permitted
c) Rutherford’s atomic model
Class: ___________
Observatory / Guide
11129-B
3
ANSWER KEY
Support activities – Second year of Secondary Cycle Two
ACTIVITY 1
The atom and atomic models