Ions

How are ions made from neutral atoms?

Why?
You have learned that not all atoms of an element are the same. Variation in the number of neutrons
results in different isotopes of the element. In this activity we will explore another variation that can take
place—the loss and gain of electrons. The exchange of electrons between atoms is a very common way for
chemical change to take place. We will see it many times throughout the year.
1. Use Model 1 to complete the following table.

Is the number of Is the number of Is the number of

Charge
Metal or protons the same neutrons the same electrons the same
on the
Nonmetal in the atom in the atom in the atom
ion
and the ion? and the ion? and the ion?
Lithium metal 1+
Magnesium 2+
Aluminum yes 3+
Fluorine no 1–
Oxygen nonmetal yes no 2–
Nitrogen 3–
2. Based on the table you completed in Question 1, what distinguishes a neutral atom from an ion?

3. Examine the isotope symbols in Model 1.

a. Where is the ion charge located in the isotope symbol?

b. Is a charge indicated on the neutral atoms? If yes, where is it located?

4. Which subatomic particle carries a positive charge?

5. Which subatomic particle carries a negative charge?

6. Propose a mathematical equation to calculate the charge on an ion from the number of protons
and electrons in an ion. Confirm that your equation works using two positive ion examples and
two negative ion examples from Model 1.

Ions 1
 Model 1 – Atoms and Ions
Neutral Atoms Ions Neutral Atoms Ions
Atom of Lithium Ion of Lithium Atom of Fluorine Ion of Fluorine
7 7 19 19 1–
Symbol Li Li1+ Symbol F F
3 3 9 9
Electron cloud Electron cloud Electron cloud Electron cloud
Nucleus Nucleus Nucleus Nucleus

Atomic Diagram Atomic Diagram

No. of Protons 3 3 No. of Protons 9 9

No. of Neutrons 4 4 No. of Neutrons 10 10
No. of Electrons 3 2 No. of Electrons 9 10
Atom of Magnesium Ion of Magnesium Atom of Oxygen Ion of Oxygen
24 24 16 16
Symbol Mg Mg 2+ Symbol O O2–
12 12 8 8
Electron cloud Electron cloud Electron cloud Electron cloud
Nucleus Nucleus Nucleus Nucleus

Atomic Diagram Atomic Diagram

No. of Protons 12 12 No. of Protons 8 8

No. of Neutrons 12 12 No. of Neutrons 8 8
No. of Electrons 12 10 No. of Electrons 8 10
Atom of Aluminum Ion of Aluminum Atom of Nitrogen Ion of Nitrogen
27 27 14 14
Symbol Al Al3+ Symbol N N3–
13 13 7 7
Electron cloud Electron cloud Electron cloud Electron cloud
Nucleus Nucleus Nucleus Nucleus

Atomic Diagram Atomic Diagram

No. of Protons 13 13 No. of Protons 7 7

No. of Neutrons 14 14 No. of Neutrons 7 7

2 POGIL™ Activities for High School Chemistry

No. of Electrons 13 10 No. of Electrons 7 10
Read This!
Chemists refer to positively charged ions as cations. Chemists refer to negatively charged ions as anions.

7. Fill in the following table.

88 32 2–
Sr2+ S
Symbol 38 16

Atomic Number 35

Mass Number 70

Number of protons 31

Number of electrons 28 36

Number of neutrons 45

Cation or anion

8. Could a +3 ion of aluminum be made by adding three protons to an aluminum atom? Explain.

9. One of your classmates is having trouble understanding ions. He explains the formation of a
cation like this:
“When you add an electron, you get a positive charge because adding is positive in math.”
a. As a group, explain in a grammatically correct sentence why this student is incorrect.

b. Provide a better description of how math relates to electrons and ion formation.

Ions 3
Model 2 – Ion Charges for Selected Elements
I II III IV V VI VII VIII

1 H+

2 Li+ N3– O2– F1–

3 Na+ Mg2+ transition elements Al3+ P3– S2– Cl1–

Fe2+ Ni2+ Cu+
4 K+ Ca2+ Zn2+ Ga3+ Br1–
Fe3+ Ni3+ Cu2+
Sn2+
5 Rb+ Sr2+ Ag1+ I1–
Sn4+
Hg22+ Pb2+
6 Ba2+
Hg2+ Pb4+
CATIONS ANIONS
10. Draw a stair-step line in Model 2 to separate the metals and nonmetals.

11. Consider the ions listed in Model 2.
a. In general, do nonmetals form anions or cations?

b. In general, do metals form anions or cations?

c. Which nonmetal appears to be an exception to these guidelines?

4 POGIL™ Activities for High School Chemistry

Extension Questions
12. Name the family of elements that make 1– anions as shown in Model 2.

13. Name the family of elements that make 2+ cations as shown in Model 2.

14. For the main group elements (excluding the transition elements), is it necessary to memorize
the type of ion each element makes or could you predict the ion charge using a periodic table?
Explain.

15. In Model 2 there are several elements whose atoms make more than one type of ion. Where in
the periodic table are these elements usually found?

Ions 5