How to Use This Lab
1. Learn
Study core definitions, electronic rules, and worked stoichiometry examples.
2. Visualise
Use Build an Atom to observe nuclear composition, shells, and valence distributions.
3. Investigate
Inspect periodic trends and multi-shell bonding dynamics across periods 1 through 4.
4. Assess
Complete diagnostic assessments to evaluate mastery and review any weak areas.
Core Concepts
Atomic Number, Z
The number of protons in the nucleus. Uniquely identifies an element.
Mass Number, A
Total count of protons and neutrons in a specific nucleus. Neutrons = A − Z.
Isotopes
Nuclides of the same chemical element possessing identical atomic numbers but different neutron totals.
Valence Electrons
Electrons in the outermost occupied quantum level that dictate bonding behavior.
Worked Example: Chlorine-35
Z = 17, A = 35. Protons = 17. Neutral electrons = 17. Neutrons = 18. Bohr configuration = 2, 8, 7. Valence electrons = 7. Chlorine forms the chloride anion Cl−.
Subshell Capacities
Calcium, Z=20: 2, 8, 8, 2 and 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².
Animated Bohr Atom Builder
Interactive model showing orbital occupancy for elements 1 to 20.
element
Interactive Periodic Table: Elements 1 to 20
Bonding Lab: Reaction Simulations
Select two elements to model orbital interaction, electron exchange, and chemical compound formation.
Mystery Element
Spot the Error
Chemistry Mastery Assessment
Answer the questions below to test your understanding across atomic structure, periodic trends, and chemical bonding.