Download 10.1 RG and answer key

Name
Date
Class
Introduction to Atoms
How Did Atomic Theory Develop?
1a.
DEFINE An atom is _______________________________________________________________
b. DESCRIBE Bohr’s model of the atom consisted of a central ____________________
surrounded by electrons moving in specific ____________________ .
c. COMPARE AND CONTRAST How is the cloud model of the atom different
from Bohr’s model?________________________________________________________________
I get it! Now I know that atomic theory changed with time because ___________________________
I need extra help with ______________________________________________________________
How Is the Modern Model of the Atom Described?
2a.
EXPLAIN What is atomic number? How is atomic number used to
distinguish one element from another? ________________________________________________
b. APPLY CONCEPTS The atomic number of nitrogen is 7. How many
protons, neutrons, and electrons make up an atom of nitrogen-15? __________________________
I get it! Now I know that the modern model of the atom can be described as ____________________
I need extra help with ______________________________________________________________
Name
Date
Introduction to Atoms
On a separate sheet of paper, describe the modern model of the atom.
Class
Name
Date
Class
Introduction to Atoms
Understanding Main Ideas
Answer the following questions on a separate sheet of paper.
1. Which two particles are found in an atom’s nucleus?
2. What three particles are found in an atom?
3. Explain why scientists use models to study atoms.
4. Which two particles in an atom are equal in number?
5. How are elements identified in terms of their atoms?
6. What two particles account for almost all of the mass of an atom?
Building Vocabulary
Fill in the blank to complete each statement.
7. The ___________________ is the very small, dense center of an atom.
8. The positively charged particle of an atom is called a(n) ___________________ .
9. A particle with no charge is a(n) ___________________ .
10. A(n) ________________ is the particle of an atom that moves rapidly in the
cloudlike region around the nucleus.
11. The ________________________________________ tells the number of protons in the
nucleus of every atom of an element.
12. Atoms of the same element that have the same number of protons but different
numbers of neutrons are called ___________________ .
13. The sum of protons and neutrons in the nucleus of an atom is the
___________________________________ .
14. Scientists will often use a(n) ___________________ , an object that helps explain ideas
about the natural world.
Name
Date
Class
Introduction to Atoms
Read the passage and study the figure below it. Then use a separate sheet of paper to
answer the questions that follow the figure.
Exactly How Small Is It?
Measuring the size of an atom is not easy. For one thing, an atom is very, very tiny. Scientists, however,
have developed several ways to estimate the relative sizes of atoms. For elements that exist as two
identical molecules bonded together, such as oxygen and hydrogen, scientists can use a technique called
X-ray diffraction to estimate the distance between the nuclei. Once scientists do that, they can calculate
the atomic radius, which is one-half the distance between the nuclei.
It’s important to remember that the atomic radius is not a measurement of a single atom’s size but
only its size relative to other atoms. In other words, scientists know that oxygen atoms are larger than
hydrogen atoms, but they don’t know the exact size of any single atom of oxygen. When comparing
sizes of atoms, one must be careful to compare sizes based on similar measuring techniques.
The figure below shows the atomic radii of several elements. The atomic radius is given in units of
picometers (pm). One picometer is equal to 0.000000000001 meter.
1. What determines the size of an atom?
2. Why is it difficult to measure the size of an atom?
3. What is the distance between nuclei in a hydrogen molecule (H2)?
4. What would be the distance between nuclei of a bromine
molecule (Br2)?
5. What is the atomic radius of oxygen in meters?
6. Which atoms are relatively larger than oxygen atoms?
Name
Date
Class
Introduction to Atoms
Write the letter of the correct answer on the line at the left.
1. ___ The positively charged particle in an
atom’s nucleus is the
2. ___ An element’s identity can be
determined from its
A
electron
A
atomic number
B
neutron
B
number of neutrons
C
proton
C
number of isotopes
D
isotope
D
energy levels
3. ___ The smallest particle an element can
be divided into is the
A
electron
B
neutron
C
isotope
D
atom
4. ___ The model of the atom that described
electrons scattered throughout a ball of
positive charge was proposed by
A
Niels Bohr
B
Ernest Rutherford
C
J. J. Thomson
D
John Dalton
If the statement is true, write true. If the statement is false, change the underlined word
or words to make the statement true.
5. _______________ An element’s mass number tells the number of protons in its
nucleus.
6. _______________ Negatively charged particles in an atom are called electrons.
7. _______________ The cloud model of the atom describes the location of
electrons as specific orbits around the nucleus.
8. _______________ Atoms with the same number of protons but different numbers
of neutrons are called isomers.
9. _______________ The sum of the protons and neutrons in an atom is called the
atomic number.
10. _______________ An object that helps explain ideas about the natural world is
called a model.
Introduction to Atoms
Answer Key
1. Sample: I used touch, sound, and smell.
2. Sample: I did not use sight and taste because
I could not see or taste the object through the
box.
3. The object must be smaller than the box
because it fits inside the box.
4. Sample: The object would make soft sounds
when the box is shaken, the box would be
light.
7.
9.
11.
13.
nucleus
neutron
atomic number
mass number
8.
10.
12.
14.
proton
electron
isotopes
model
1. The space taken up by the electrons determine
the size of an atom.
2. Sample: atoms are very small, do not have
definite boundary lines, and change size
depending on their physical state and whether
or not they are bonded to another atom.
3. 37 pm × 2 = 74 pm
According to the modern model of the atom,
the center of the atom is a tiny, dense nucleus
containing protons (positively charged particles)
and neutrons (neutral particles). Surrounding
the nucleus is a cloudlike region of electrons
(negatively charged particles), whose movements
are related to their energy levels. The number of
protons in the nucleus of an atom of an element
is called the atomic number. The atomic number
defines an element. The number of protons is
equal to the number of electrons. Protons and
electrons account for almost all of the mass of an
atom. Mass number is the number of protons and
neutrons. Isotopes are atoms of the same element
that have different mass numbers because they
have different numbers of neutrons.
1. proton, neutron, electron
2. protons and neutrons
3. Scientists use models to study atoms because
atoms are so small.
5. protons and electrons
5. An element can be identified by the number
of protons in the nucleus of its atom.
6. protons and neutrons
4. 114 pm × 2 = 228 pm
5. 66 pm = 0.000000000066 m
6. Nitrogen and bromine atoms are relatively
larger than oxygen atoms.
1.
3.
5.
7.
9.
C
D
atomic
Bohr
mass
2.
4.
6.
8.
10.
A
C
true
isotopes
true