Michigan Test for Teacher Certification (MTTC) Secondary Integrated Science Practice test

What characterizes ions?

1. Equal number of protons and electrons

2. Unequal number of protons and electrons

3. Only positively charged particles

4. Stable neutral particles

The correct answer is: Unequal number of protons and electrons

Ions are characterized by having an unequal number of protons and electrons. This imbalance results in a net electric charge; if there are more protons than electrons, the ion carries a positive charge and is called a cation. Conversely, if there are more electrons than protons, the ion carries a negative charge and is known as an anion. This fundamental property of ions differentiates them from neutral atoms, which possess an equal number of protons and electrons, resulting in no overall charge. The other choices do not accurately reflect the definition of ions. Neutral particles, by definition, have an equal number of protons and electrons and therefore do not represent ions. Similarly, ions can be either positively or negatively charged, so the statement that they are only positively charged is not true. A balanced configuration with an equal number of protons and electrons describes stable neutral atoms rather than ions.