Name
KEY
Period
Chapter 4 – Atomic Structure
Short Answer: Answer the following questions in complete sentences using science
vocabulary. Make sure that your answers are complete and detailed.
1. A sample of calcium contains calcium-40, calcium-44, calcium-42, calcium-48, calcium43, and calcium-46 atoms. Explain why these atoms have different mass numbers but
must have the same atomic number.
The atoms have different mass numbers because they have a different number of
neutrons. The mass number is equaled to the number of protons plus neutrons.
The atoms must have the same atomic number because the atomic number is
equaled to the number of protons. The number of protons is unique for each element.
2. Complete the following table. Circle the name of the element(s) that are isotopes.
Complete Bohr’s Model diagrams for the element with eleven electrons and the element
with an atomic number of 9.
Element
Name
Element
Symbol
Atomic
Number
Mass
Number
Protons
Neutrons
Electrons
Scandium
Sc
21
45
21
24
21
Fluorine
F
9
19
9
10
9
Na
11
24
11
13
11
Sodium
Answers
Vary
82
3. What is the difference between the atomic number of an atom and its mass number?
The atomic number is the number of protons in an element. Since the number of
electrons is the same as the number of protons, the atomic number also equals the
number of electrons.
The mass number is equaled to the number of protons plus neutrons.
4. Explain why a neutral atom cannot have one proton, one neutron, and two electrons?
Protons have a positive charge (+) and electrons have a negative charge (-).
Neutrons have no charge. Therefore, a neutral atom cannot have more electrons
than protons, as it would have an overall negative charge (-1).
5. The nucleus of an atom contains six neutrons and six protons. The nucleus of a second
atom contains six neutrons and five protons. Are they atoms of different elements or
isotopes of the same element? Explain you answer.
The atoms are different elements, since they have different numbers of protons. The
first atom has six protons and is therefore carbon. The second atom has five protons
and is therefore boron.
6. Brightly colored neon lights consist of tubes filled with a gas. When an electric current
passes through the tubes, different colors are emitted. Why might you conclude that the
tubes in a multicolored display contain more than one element?
From the flame test lab, we discovered that different elements and/or compounds
emit different colors of light. Therefore, if the “neon” light emitted different colored
lights, we can conclude that the lights contain different elements and/or compounds.