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🔬 PERIODIC TABLE – IMPORTANT CONCEPTS (EXAM ORIENTED)
1️⃣ Modern Periodic Law
👉 The physical and chemical properties of elements are periodic functions of their atomic numbers.
✔️ Arranged in increasing atomic number
❌ Not on atomic mass (old law)
2️⃣ Structure of Periodic Table
Periods → Horizontal rows (7 periods)
Groups → Vertical columns (18 groups)
Part
Meaning
Period
Number of shells
Group
Number of valence electrons (s & p block)
3️⃣ Blocks of Periodic Table (VERY IMPORTANT)
Based on valence orbital
Block
Groups
Elements
s-block
1–2
Alkali & Alkaline earth metals
p-block
13–18
Non-metals, metalloids
d-block
3–12
Transition metals
f-block
Inner transition metals
👉 Lanthanides (57–71)
👉 Actinides (89–103)
4️⃣ Group-wise Important Facts (Most Asked)
🔹 Group 1 – Alkali Metals
Li, Na, K, Rb, Cs
✔️ Soft, highly reactive
✔️ Valency = 1
✔️ Stored in kerosene
🔹 Group 2 – Alkaline Earth Metals
Be, Mg, Ca
✔️ Valency = 2
✔️ Harder than alkali metals
🔹 Group 17 – Halogens
F, Cl, Br, I
✔️ Non-metals
✔️ Valency = 1
✔️ Very reactive
🔹 Group 18 – Noble Gases
He, Ne, Ar
✔️ Zero valency
✔️ Inert gases
✔️ Monoatomic
5️⃣ Periodic Trends (EXAM FAVORITE ⭐)
🔺 Atomic Size
Increases ↓ group
Decreases → period
🔺 Metallic Character
Increases ↓ group
Decreases → period
🔺 Non-metallic Character
Decreases ↓ group
Increases → period
🔺 Ionization Energy
Decreases ↓ group
Increases → period
🔺 Electronegativity
Highest → Fluorine (F)
Increases → period
Decreases ↓ group
6️⃣ Valency Rules
Group 1 → Valency 1
Group 2 → Valency 2
Group 13 → Valency 3
Group 14 → Valency 4
Group 15 → Valency 3/5
Group 16 → Valency 2
Group 17 → Valency 1
Group 18 → Valency 0
7️⃣ Metals, Non-metals & Metalloids
Metals → Left side
Non-metals → Right side
Metalloids → Zig-zag line
(B, Si, Ge, As)
8️⃣ Hydrogen – Special Case ⚠️
✔️ Atomic number = 1
✔️ Resembles Group 1 & Group 17
✔️ Placed separately
9️⃣ Most Important One-Liners (Rapid Revision)
✔️ He is the lightest noble gas
✔️ Cs is the most reactive metal
✔️ F is the most electronegative element
✔️ Na is essential for nerve impulse
✔️ Ca is important for bones
🔟 Exam Tips 🎯
Questions mostly from trends + groups
Remember F, Cs, He special properties
Valency & blocks are high-scoring
