Ion Examples in Chemistry

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Ion.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Chemistry.

Concept Recap

An atom or group of atoms that has gained or lost one or more electrons, resulting in a net positive charge (cation) or net negative charge (anion). The number of protons remains unchanged; only the electron count changes.

An atom that's not neutral—it has more or fewer electrons than protons.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Cations are positive (lost electrons), anions are negative (gained electrons).

Common stuck point: The number of protons never changes when forming an ion — only the number of electrons changes to create the charge.

Sense of Study hint: When determining the charge of an ion, compare electrons to protons. First find the number of protons from the atomic number. Then count the electrons (given or inferred from the electron configuration). Finally, calculate charge = protons - electrons. Positive means cation, negative means anion.

Worked Examples

Example 1

easy
Sodium (Z = 11) loses one electron. Write the ion formed and its electron configuration.

Solution

  1. 1
    Neutral Na: 1s^2\,2s^2\,2p^6\,3s^1 (11 electrons).
  2. 2
    Losing 1 electron: \text{Na}^+ with configuration 1s^2\,2s^2\,2p^6 (10 electrons).
  3. 3
    This is the same electron configuration as neon (isoelectronic with Ne).

Answer

\text{Na}^+:\; 1s^2\,2s^2\,2p^6
Metals tend to lose electrons to form cations. Sodium loses its single valence electron to achieve the stable noble gas configuration of neon.

Example 2

medium
An unknown ion has 10 electrons, 8 protons, and 8 neutrons. Identify the element, write the ion symbol, and calculate its charge.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Predict the ion formed by each: (a) calcium, (b) fluorine, (c) aluminum.

Example 2

medium
Aluminum loses 3 electrons. What ion forms, and why is its charge positive?
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Background Knowledge

These ideas may be useful before you work through the harder examples.

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