Question

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Chemists refer to positively charged ions as cations. Chemists refer to negatively charged ions as anions.
7. Fill in the following table.
Symbol
Atomic Number
Mass Number
Number of protons
Number of electrons
Number of neutrons
Cation or anion
88.
38
Sr2+
16
70
31
28
35
36
45
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.

Answer 1

To understand ions, we must recognize that cations form through the loss of electrons and have a positive charge, while anions form by gaining electrons and have a negative charge. The atomic charge is determined by subtracting the number of electrons from the number of protons. Therefore, adding electrons results in a negative charge, not a positive one.

Understanding Ions and Ionic Bonding

Chemists refer to positively charged ions as cations, and to negatively charged ions as anions. The formation of ions involves the gain or loss of electrons. A cation forms when an atom loses one or more electrons, resulting in more protons than electrons and thus a positive charge. Conversely, an anion forms when an atom gains one or more electrons, giving it a negative charge.

An atom's atomic charge can be calculated using the formula: atomic charge = number of protons - number of electrons. For example, the aluminum ion Al³+ becomes a cation by losing three electrons, not by adding protons. It has 13 protons (atomic number of aluminum) and now only 10 electrons.

To correct a student's misunderstanding, you might explain that: "You do not get a positive charge by adding an electron; in fact, adding an electron to an atom results in a negative charge, since electrons are negatively charged." A more precise mathematical relationship in this context would be subtracting electrons leads to cations (positive charge), while adding electrons leads to anions (negative charge).

In the formation of ions, metals typically form cations while nonmetals form anions. The ion's name is often derived from the element, with cations keeping the element name, and anions changing the ending to '-ide'.