Interactive Class 10 CBSE Chemistry assistant: Explore Bohr-Bury electronic configurations, valencies, atomic radii, metallic trends, and reasons behind group and period placements.
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🎓 Class 10 CBSE Scope● Focused on Core 1–20 + Board Exam Metals
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P1
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57–71La–Lu
P7
89–103Ac–Lr
* La
** Ac
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Visual Trends Explorer
Periodic Trends in the Modern Periodic Table
High-Yield Class 10 Board Exam Topic
Across a Period (Left to Right)📉 Decreases →
Generally DECREASES from left to right across a period.
CBSE Scientific Reason:
Across a period, electrons are added to the same outermost shell while the positive nuclear charge (number of protons) increases progressively. This creates a stronger electrostatic pull from the nucleus, pulling the electron clouds closer and shrinking the atomic size.
Down a Group (Top to Bottom)📈 Increases ↓
Generally INCREASES from top to bottom down a group.
CBSE Scientific Reason:
Down a group, a completely new electron shell is added with each successive period. This increases the physical distance between the nucleus and the outermost shell, which outweighs the increase in nuclear charge, resulting in larger atomic size.
Live Sequence across Period 3:
Z=11Na186 pm
Z=12Mg160 pm
Z=13Al143 pm
Z=14Si118 pm
Z=15P110 pm
Z=16S103 pm
Z=17Cl99 pm
Z=18Ar98 pm
Bohr-Bury Shell Calculator
Find Element by Electronic Configuration
Enter K, L, M, N shell distributions
Class 10 Presets:
11Na
Sodium (Na)
Atomic Number Z = 11 · ALKALI METAL
Occupied Shells3 (Period 3)
Valence Electrons1 e⁻
Group in TableGroup 1
Class 10 ValencyValency 1
💡 Why? Total electrons = 11. Number of occupied shells = 3 placing it in Period 3. Outermost electrons = 1 placing it in Group 1.
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Question 1 of 12Score: 0
An element has electronic configuration 2, 8, 7. What is its identity and atomic number?