Skip to content

Atomic Structure Diagram

Run the Atomic Structure Diagram MicroSim Fullscreen

About This MicroSim

This MicroSim displays a stylized cross-section of an atom on a dark navy background. The nucleus is shown as a compact cluster of red protons and gray neutrons. Concentric dashed ellipses represent electron shells, with blue dots orbiting on each shell according to the standard electron configuration rules (2, 8, 8 for the first three shells).

A slider at the bottom controls the Atomic Number (Z) from 1 (Hydrogen) to 18 (Argon). As Z changes:

  • The nucleus grows with more protons and neutrons
  • Additional electron shells populate automatically
  • The legend panel updates live with the element symbol, name, and particle counts
  • Shell-by-shell electron configuration is displayed

Hovering over individual nucleus particles triggers a tooltip showing "Proton (+1)" or "Neutron (0)". Electron orbit animation activates when the mouse is over the canvas.

How to Use

  1. Load — The simulation opens with Carbon (Z = 6) as the default element.
  2. Slide — Drag the Atomic Number slider left or right to change the element.
  3. Observe — Watch the nucleus grow, shells fill, and the legend update in real time.
  4. Hover — Move your cursor over nucleus particles to identify protons (red) and neutrons (gray).
  5. Predict — Before moving the slider, predict how the electron configuration will change.

Iframe Embed Code

1
2
3
4
<iframe src="https://dmccreary.github.io/chemistry/sims/atomic-structure-diagram/main.html"
        height="442px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Grade Level

9–12 (AP Chemistry, Chapter 2)

Duration

10–15 minutes

Learning Objectives

  • L1 Remembering: Identify the location, charge, and relative mass of protons, neutrons, and electrons within an atom.
  • L2 Understanding: Explain how the atomic number (Z) determines elemental identity and how electrons fill shells according to the 2-8-8 rule.

Prerequisites

  • Basic understanding of atoms and elements
  • Familiarity with the periodic table (symbols and names)

Activities

  1. Exploration (3 min): Open the MicroSim. Slide Z from 1 to 18 and observe how the nucleus and electron shells change. Ask: What pattern do you notice in how electrons fill the shells?
  2. Guided Practice (5 min): Set Z = 8 (Oxygen). Hover over nucleus particles. Ask students: How many protons? How many neutrons? How do you know which is which?
  3. Compare Elements (5 min): Compare Z = 10 (Neon) and Z = 11 (Sodium). Ask: Why does sodium have a third shell? What makes neon chemically stable?
  4. Assessment (2 min): Given a mystery Z value, have students predict the electron configuration before checking with the slider.

Assessment

  • Can the student correctly read the proton and neutron count from the legend?
  • Can the student predict which shell the next electron will fill?
  • Can the student explain why two elements with adjacent Z values have different chemical properties?

References

  1. College Board AP Chemistry Course and Exam Description (CED), Unit 1: Atomic Structure and Properties.
  2. Zumdahl, S. S. & DeCoste, D. J. Chemistry: An Atoms First Approach, 3rd ed. Cengage, 2020.
  3. OpenStax Chemistry 2e, Chapter 2: Atoms, Molecules, and Ions. openstax.org