Electron Examples in Chemistry

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

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

Concept Recap

A negatively charged subatomic particle with negligible mass that occupies energy levels (shells) outside the nucleus.

The particles that do the 'dancing'—they're what's involved in bonding and reactions.

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: Electrons determine how atoms bond and react — all of chemistry is electron behavior.

Common stuck point: Electrons have almost no mass compared to protons/neutrons, yet they govern all chemical properties.

Sense of Study hint: When working with electrons, count them carefully. First for a neutral atom, electrons equal the atomic number (proton count). Then for ions, add electrons for negative charges and subtract for positive charges. Finally, fill electron shells from lowest to highest energy following the Aufbau principle.

Worked Examples

Example 1

easy
Write the electron configuration for oxygen (Z = 8).

Solution

  1. 1
    Oxygen has atomic number 8, so a neutral oxygen atom has 8 electrons. Fill orbitals using the Aufbau principle in order of energy: 1s, then 2s, then 2p.
  2. 2
    Fill each subshell to its maximum capacity: 1s^2 (2 electrons), 2s^2 (2 electrons), leaving 8 - 4 = 4 electrons for the 2p subshell.
  3. 3
    Write the complete electron configuration: 1s^2\,2s^2\,2p^4. Verify: 2 + 2 + 4 = 8 total electrons.

Answer

1s^2\,2s^2\,2p^4
Electron configurations show how electrons are distributed among energy levels and orbitals. They follow the Aufbau principle, filling lower-energy orbitals first.

Example 2

medium
A chlorine atom (Z = 17) gains one electron. Write the electron configuration of the resulting \text{Cl}^- ion and explain why chlorine tends to gain an electron.

Practice Problems

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

Example 1

easy
How many electrons does a neutral atom of magnesium (Z = 12) have? Write its electron configuration.

Example 2

medium
Which subatomic particle is mainly responsible for chemical bonding, and why?
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Background Knowledge

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

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