Metals, Non-Metals & Metalloids
Elements are classified as:
- 🔥 Metals (78% of elements): Left side of periodic table.
→ Solids at room temperature (except mercury, gallium, cesium)
→ High melting/boiling points, conduct heat/electricity
→ Malleable (flattened) & ductile (drawn into wires) - 💨 Non-metals: Top-right of periodic table
→ Solids/gases at room temperature (mostly)
→ Low melting/boiling points, poor conductors
→ Brittle (break easily) - ⚖️ Metalloids (e.g., Si, Ge): Borderline elements with properties of both metals & non-metals
Trends in Properties
| Property | Across Period (→) | Down Group (↓) |
|---|---|---|
| Atomic Radius | Decreases ⬇️ (e.g., Li 152pm → F 64pm) | Increases ⬆️ (e.g., F 64pm → I 133pm) |
| Ionization Energy (Energy to remove electron) | Increases ⬆️ (Harder to remove electrons) | Decreases ⬇️ (Easier to remove electrons) |
| Electron Gain Enthalpy (Energy change adding electron) | More negative ⬇️💥 (Easier to gain electrons) | Less negative ⬆️ (Harder to gain electrons) |
| Electronegativity (Ability to attract electrons) | Increases ⬆️ (e.g., Li 1.0 → F 4.0) | Decreases ⬇️ (e.g., F 4.0 → I 2.5) |
Key Relationships
- Smaller atomic size = Higher ionization energy ⬆️
- Higher nuclear charge = Smaller atomic radius ⬇️
- Metallic character ↓ across period, ↑ down group
Special Cases & Anomalies
- 💡 Ionic vs Atomic Size:
→ Cations are smaller than parent atom (Na: 186pm → Na⁺: 95pm)
→ Anions are larger than parent atom (F: 64pm → F⁻: 136pm) - 🔍 Isoelectronic Species (same electrons):
Size order: O²⁻ > F⁻ > Na⁺ > Mg²⁺ (greater positive charge = smaller size) - ⚠️ Boron Exception: Lower ionization energy than beryllium due to easier removal of p-electron vs s-electron.
Chemical Behavior
- 🧪 Oxides:
→ Left elements: Basic oxides (Na₂O + H₂O → NaOH)
→ Right elements: Acidic oxides (Cl₂O₇ + H₂O → HClO₄)
→ Center elements: Amphoteric/neutral (Al₂O₃, CO) - 🧲 Valence Trends:
Group 1: Valence 1 (LiH, Na₂O)
Group 16: Valence 2/6 (H₂O, SO₃)
NEET Highlights 🔥
- Atomic/Ionic Radius Trends: Decrease across period, increase down group
- Ionization Energy Order: Noble gases > halogens > alkali metals
- Electronegativity Scale: F (4.0) highest, Fr (0.7) lowest
- Isoelectronic Size Comparison: More positive charge = smaller size
- Anomalous Behavior: Li/Be show covalent character (unlike group)
Quick Summary
Periodic trends repeat predictably! Remember:
• Left → Right: Size ↓, Ionization ↑, Metallic ↓
• Top → Bottom: Size ↑, Ionization ↓, Metallic ↑
• Reactivity peaks at extremes (alkali metals & halogens)
