Electron Configuration – Atoms Z = 1–36
ChemistryAtomic Structure & Periodic TableAges 15–16
Use it with your class: students open it from a link or a QR code, with no account needed.
Next in Atomic Structure & Periodic Table
Pick an element on the mini periodic table and watch its electrons fill the shells (Bohr model) and orbital boxes according to the Aufbau principle, the Pauli exclusion principle, and Hund's rule. The sim shows the full and condensed electron configuration, the number of valence electrons, period, group, block, and predicts whether the element is a metal or a nonmetal.
Lesson: Atomic electron shell structure – electron configuration
What it shows
Electrons fill orbitals according to three rules: the Aufbau principle (lowest-energy subshell first), the Pauli exclusion principle (at most two electrons of opposite spin per orbital) and Hund's rule (electrons in a subshell occupy separate orbitals before pairing). Because 4s is lower in energy than 3d, it fills first, which is why potassium and calcium begin period 4. The simulation covers hydrogen to krypton, including the chromium and copper exceptions, and links each configuration to the element's period, group, block and likely metallic or nonmetallic character.
How to use
Set the Atomic number Z and press Fill Step by Step, with a low Fill speed so you can pause and ask where the next electron goes. Use Z + 1 ▶ to walk along a period. Compare Full and Condensed notation, and show the Bohr shell model to connect orbital boxes with shells. Look closely at Z = 19 to 21, 24 and 29.
Parameters you can change
- Atomic number Z 1–36
- Fill electrons step by step on open
- Fill speed 1–10 electron/s
- Configuration notation Full, Condensed (noble gas core)
- Show electron shell model (Bohr)
Questions to explore
- How many unpaired electrons does a nitrogen atom have, and which rule explains this?
- Why is the configuration of chromium [Ar]3d⁵4s¹ rather than [Ar]3d⁴4s²?
- An element has 7 electrons in its outer shell. Is it more likely to be a metal or a nonmetal?
Common questions
How do you write the electron configuration of an element?
Place the element's Z electrons into subshells in order of increasing energy, filling each before moving on: 1s, 2s, 2p, 3s, 3p and so on. An s subshell holds 2 electrons and a p subshell holds 6. Sulfur, Z = 16, is 1s²2s²2p⁶3s²3p⁴, or [Ne]3s²3p⁴ in condensed notation with a noble gas core.
What is the difference between a shell, a subshell and an orbital?
A shell is a main energy level numbered n, a subshell is a group of orbitals of one type inside it (s, p, d or f), and an orbital is a region that holds at most 2 electrons. Subshells s, p and d have 1, 3 and 5 orbitals, so they hold 2, 6 and 10 electrons. A shell holds up to 2n² electrons.
How do you find the period and group of an element from its electron configuration?
The period equals the highest shell number in the configuration, and the group follows from the outer electrons. In the s-block the group equals the number of outer s electrons, and in the p-block it is 10 plus the outer s and p electrons. Chlorine, [Ne]3s²3p⁵, has 7 such electrons, so it is in period 3, group 17.
