Introduction to Modern Periodic Table
Welcome to Lecture 11 of the CHEMCA Bridge Course! Inorganic chemistry is fundamentally driven by the arrangement of elements. In this session, Abhishek Sengar Sir introduces the Modern Periodic Table. Learn how the modern table is organized around Atomic Numbers ($Z$), discover the 4 block subshells ($s, p, d, f$), and find out how magic numbers determine the element capacities of periods.
Video Lecture Broadcast
Interactive Lecture Timestamps
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In-Depth Lecture Notes & Summary
Mendeleev vs. Modern Periodic Law
Early attempts at classifying elements (such as Dobereiner's Triads, Newlands' Octaves, and Mendeleev's Periodic Table) were based strictly on Atomic Mass. However, this caused numerous anomalies, such as placing heavier elements before lighter ones.
The Modern Periodic Law
"The physical and chemical properties of the elements are periodic functions of their Atomic Numbers ($Z$)."
Proposed by Henry Moseley, sorting elements by atomic number ($Z$) aligned them perfectly with their electronic configurations, resolving almost all historical classification flaws.
Periods, Groups & Subshell Blocks
The Modern Periodic Table organizes elements into 7 Horizontal Rows (Periods) and 18 Vertical Columns (Groups), categorized into 4 subshell blocks:
- s-block (Groups 1 & 2): Outer electrons fill the $s$-subshell. Very reactive metals.
- p-block (Groups 13 to 18): Outer electrons fill the $p$-subshell. Includes metals, metalloids, and non-metals.
- d-block (Groups 3 to 12): Outer electrons fill the inner $(n-1)d$ subshell. Known as Transition Metals.
- f-block (Placed below): Outer electrons fill the $(n-2)f$ subshell. Known as Inner Transition Elements.
Special Names of Chemical Families
Specific groups contain chemically similar families with special historical names:
Alkali Metals
Alkaline Earth
Coinage Metals
Pnictogens
Chalcogens
Halogens
Noble Gases
The Magic Numbers ($2, 8, 8, 18, 18, 32, 32$)
The capacities of periods are governed by quantum subshell energy limits. Adding the capacities of filled subshells in each period reveals the Magic Numbers of elements per period:
- Period 1 (Shortest): $2$ elements ($1s$) $\implies$ $Z=1$ to $2$.
- Period 2 (Short): $8$ elements ($2s, 2p$) $\implies$ $Z=3$ to $10$.
- Period 3 (Short): $8$ elements ($3s, 3p$) $\implies$ $Z=11$ to $18$.
- Period 4 (Long): $18$ elements ($4s, 3d, 4p$) $\implies$ $Z=19$ to $36$.
- Period 5 (Long): $18$ elements ($5s, 4d, 5p$) $\implies$ $Z=37$ to $54$.
- Period 6 (Very Long): $32$ elements ($6s, 4f, 5d, 6p$) $\implies$ $Z=55$ to $86$. Includes Lanthanides ($Z = 58$ to $71$ in 4f series).
- Period 7 (Very Long): $32$ elements ($7s, 5f, 6d, 7p$) $\implies$ $Z=87$ to $118$. Includes Actinides ($Z = 90$ to $103$ in 5f series).
Magic Numbers Period Finder
Input a Period Number ($1$ to $7$) to explore subshell configurations and atomic capacities.
Period Details: Long
Mnemonic Cheat Sheets
Click below to view the Hindi memorization phrases Abhishek Sir teaches in class!
"He Li Na Ki Rub Se Faryad"
Elements: H, Li, Na, K, Rb, Cs, Fr
"Beta Mange Car Scooter Baap Raazi"
Elements: Be, Mg, Ca, Sr, Ba, Ra
"Fir Se Bahar Aayi Aunty"
Elements: F, Cl, Br, I, At
Lecture 11 Concept Test
Validate your understanding of groups, periods, and the modern periodic law instantly.
Stuck on Blocks?
If you are struggling to identify why certain elements are placed in the d-block or f-block, drop a message to Abhishek Sengar Sir!
Email Support →The Interactive Periodic Table
Click or hover over any element. Filter using the buttons to watch matching subshells glow.
This cleared up my confusion, thanks!
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