Chemistry Atomic Worksheet With Answers Page 2
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1
24. Refer to your periodic table.
a. How many protons are in all chlorine (Cl) atoms?
17
b. A student says “I think that some chlorine atoms have 16 protons.” Explain why this student is not correct.
ALL CHLORINE ATOMS HAVE 17 PROTONS. IF THE ATOM HAS 16 PROTONS, IT IS SULFUR.
5. Refer again to Model 1. In the isotope symbol of each atom, there is a superscripted (raised) number. This number is
also used in the name of the atom (i.e., carbon-12). It is called the mass number.
a. How is the mass number determined?
NUMBER OF PROTONS + NUMBER OF NEUTRONS
b. Why is this number called a “mass” number?
PROTONS AND NEUTRONS MAKE UP THE MASS OF
THE ATOM BECAUSE THEY EACH HAVE A MASS OF 1 AMU.
6. Fill in the table for Atom I and Atom II shown to the right.
Atom I
Atom II
Number of Protons
5
9
Number of Neutrons
6
7
Mass Number
11
16
7. Refer to Model 1.
a. Which corner of the isotope symbol contains the mass number?
TOP LEFT
b. How is the mass number of an isotope expressed in the name of an atom?
AFTER THE NAME
8. Write an isotope symbol (similar to those in Model 1) for each of the atoms in Question 6.
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��
��
Atom I -
Atom II -
��
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9. Write the name of the atom (similar to those in Model 1) for each of the atoms in Question 6.
Atom I –
Boron-11
Atom II –
Fluorine-16
10. Fill in the following table.
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Isotope Symbol
��
����
Atomic Number
19
9
16
Mass Number
40
18
31
Number of Protons
19
9
16
Number of Neutrons
21
9
15
11. Consider the examples in Model 1.
a. Do all isotopes of an element have the same atomic number? Give at least 1 example or counter-example from
Model 1 that supports your answer.
YES, CARBON-12 AND CARBON-13 ARE ISOTOPES OF CARBON
AND HAVE THE SAME ATOMIC NUMBER.
b. Do all isotopes of an element have the same mass number? Give at least 1 example or counter-example from
Model 1 that supports your answer.
NO, CARBON-12 AND CARBON-13 ARE ISOTOPES OF CARBON
BUT HAVE DIFFERENT MASS NUMBERS.
12. Considering your answers to Question 11, work with your group to write a definition of isotope using a sentence.
ISOTOPES ARE ATOMS OF THE SAME ELEMENT WITH DIFFERENT MASS NUMBERS.
13. Consult the following list of isotopes symbols:
a. Which of the atoms represented by these symbols are isotopes of each other?
ALL THE Pb’s AND Br’s
b. Which part(s) of the isotope symbol was the most helpful in answering part a of this question?
ELEMENT SYMBOL AND ATOMIC NUMBER
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