Atomic Structure (IGCSE)
Year 10 (IGCSE) ⚛️ Particles & Structure Write electron configurations; define isotopes; calculate atomic mass.
⚛️ Electron Configurations
For IGCSE, write electron configurations as comma-separated shell counts (e.g. 2,8,1 for Na).
Na (Z=11): 2,8,1 → Group 1, Period 3
Cl (Z=17): 2,8,7 → Group 7, Period 3
Ca (Z=20): 2,8,8,2 → Group 2, Period 4
Cl (Z=17): 2,8,7 → Group 7, Period 3
Ca (Z=20): 2,8,8,2 → Group 2, Period 4
🔬 Isotopes & Relative Atomic Mass
Relative Atomic Mass
$$A_r = \frac{\sum(\text{isotope mass} \times \% \text{ abundance})}{100}$$Chlorine: ³⁵Cl (75%) + ³⁷Cl (25%)
Ar = (35×75 + 37×25)/100 = 35.5
Ar = (35×75 + 37×25)/100 = 35.5
🔋 Ions
Atoms form ions by gaining or losing electrons. The number of protons determines the element — it never changes.
Na → Na⁺ + e⁻: 11p, 10e → charge +1
Cl + e⁻ → Cl⁻: 17p, 18e → charge −1
Al³⁺: 13p, 10e → charge +3
Cl + e⁻ → Cl⁻: 17p, 18e → charge −1
Al³⁺: 13p, 10e → charge +3
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Interactive Demonstration — Atomic Structure (IGCSE)
Explore atomic structure with sub-atomic particles and electron configuration.
⚛️ Electron Configuration & Isotopes
Calculate sub-atomic particle numbers from atomic/mass number.