Periodic Trends – Atomic Radius & First Ionization Energy
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Periodic Trends – Quick Definition (Paper 1 & 6)
Periodic trends are regular patterns in properties (atomic radius, ionization energy, electronegativity) across periods and down groups due to changing nuclear charge and shielding effect.
Periodic trends are regular patterns in properties (atomic radius, ionization energy, electronegativity) across periods and down groups due to changing nuclear charge and shielding effect.
1. Atomic Radius Trend – Memorise This Table (8–12 marks every year)
| Trend | Direction | Reason (Exact Exam Answer) |
|---|---|---|
| Across Period 3 (Na → Ar) | Decreases | Same shell, increasing nuclear charge pulls electrons closer |
| Down Group 1 & Group 7 | Increases | Extra shell added → greater shielding → outer electrons farther from nucleus |
2. First Ionization Energy Trend – Most Important 10-marker
| Trend | Direction | Reason (Full Marks Answer) |
|---|---|---|
| Across Period 3 | Generally increases | Increasing nuclear charge, same shielding → harder to remove electron |
| Dip between Mg→Al | Al lower than Mg | Al loses 3p electron (higher energy) vs Mg loses 3s |
| Dip between P→S | S lower than P | S has paired electron in 3p → repulsion makes removal easier |
| Down Group 1 & Group 7 | Decreases | Atomic radius ↑ + shielding ↑ → outer electron easier to remove |
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Past Paper Solutions – Periodic Trends Questions
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