🔥 Group 1: Alkali Metals
Properties, Trends, and Exam-Focused Concepts
Group 1 elements, also called alkali metals, occupy the first group of the periodic table. They are among the most reactive elements and have numerous important applications in modern chemistry. All Group 1 metals have one valence electron in their outermost s orbital.
📊 Group 1 Elements
| Element | Symbol | Atomic # | Electron Config | Reactivity |
|---|---|---|---|---|
| Lithium | Li | 3 | [He] 2s¹ | Moderate |
| Sodium | Na | 11 | [Ne] 3s¹ | High |
| Potassium | K | 19 | [Ar] 4s¹ | Very High |
| Rubidium | Rb | 37 | [Kr] 5s¹ | Extremely High |
| Cesium | Cs | 55 | [Xe] 6s¹ | Extremely High |
| Francium | Fr | 87 | [Rn] 7s¹ | Most Reactive |
⚙️ Characteristic Properties
🎯 Physical Properties
- ✨ Soft metals (easy to cut with knife)
- ⚖️ Low density (Li floats on water!)
- 🔆 Shiny surface that tarnishes quickly in air
- 🌡️ Low melting points (Li: 180°C, Na: 98°C)
- ⚡ Good electrical and thermal conductivity
🔬 Chemical Properties
🧪 Important Compounds
🧂 Sodium Compounds
- NaCl - Table Salt (preservative)
- NaOH - Caustic Soda (soap production)
- Na₂CO₃ - Wash Soda (detergent)
- NaHCO₃ - Baking Soda (leavening agent)
🥔 Potassium Compounds
- KCl - Fertilizer, food additive
- KMnO₄ - Permanganate (oxidizer)
- K₂Cr₂O₇ - Dichromate (orange oxidizer)
- K₂SO₄ - Sulfate (alum production)
📈 Periodic Trends in Group 1
📏 Atomic Radius
Increases ↓
Li < Na < K < Rb < Cs < Fr
Why: More electron shells increase atomic size
⚡ Ionization Energy
Decreases ↓
Li > Na > K > Rb > Cs > Fr
Why: Easier to remove valence electron from heavier elements
🔗 Electronegativity
Decreases ↓
Li (0.98) > Na (0.93) > K (0.82) > Rb (0.82) > Cs (0.79) > Fr (0.7)
Why: Lower electronegativity with increasing size
🔥 Reactivity
Increases ↓
Why: Decreasing ionization energy + increasing size
📚 Exam Preparation Tips
🎯 JEE Focus
- Remember flame test colors for identification
- Understand why reactivity increases down the group
- Master redox reactions with alkali metals
- Know industrial uses: Na for extracting metals
- Study lithium anomalies (high charge density)
🧬 NEET Focus
- Biological importance: Na and K for nerve impulses
- Na-K pump: maintains cell potential
- Dietary requirement: ~2-3g Na/day, 1.6-2g K/day
- Deficiency effects: muscle weakness, irregular heartbeat
- Osmotic and ionic balance in cells
📖 Board Exam Focus
- Simple properties: soft, low density, highly reactive
- Water reaction: 2M + 2H₂O → 2MOH + H₂↑
- Common uses: Na in street lamps, K in fertilizers
- Storage: kept in mineral oil (prevents air/water reaction)
- Uses of compounds: NaCl, NaOH, K₂SO₄
💡 Memorable Mnemonics
Element Order: "Li Na K Rb Cs Fr" (LiNaKRbCsFr)
Reactivity: "Alkali going Soft" - All are soft, get MORE reactive down the group
Water Reaction: "2M + 2H₂O → 2MOH + H₂↑" - Universal pattern for ALL Group 1 metals
Storage: "Olive Oil keeps Alkali Metals Safe" - Store in mineral oil to prevent oxidation