Modern Periodic Law & Table Structure
🎯 Remember: Modern Periodic Law states that properties of elements are periodic functions of their atomic numbers (not atomic mass!). This happened after scientists discovered atomic structure.
💡 Key NEET Concept: Atomic number (Z) = Nuclear charge = Proton count = Electron count in neutral atoms
Periodic Table Layout
- 📏 Rows = Periods (7 total)
- 📐 Columns = Groups (numbered 1-18 by IUPAC)
- Period number = Highest principal quantum number (\(n\)) in that row
| Period | Elements | Orbitals Filled |
|---|---|---|
| 1 | 2 | 1s |
| 2 | 8 | 2s, 2p |
| 3 | 8 | 3s, 3p |
| 4 | 18 | 4s, 3d, 4p |
| 5 | 18 | 5s, 4d, 5p |
| 6 | 32 | 6s, 4f, 5d, 6p |
| 7 | Incomplete | 7s, 5f, 6d, 7p |
✨ Special placement: Lanthanoids & actinoids are shown separately at the bottom (they fit in periods 6 & 7).
Naming Superheavy Elements (Z > 100)
🔬 For newly discovered elements, IUPAC uses temporary systematic names based on atomic number digits:
| Digit | Root | Abbrev. |
|---|---|---|
| 0 | nil | n |
| 1 | un | u |
| 2 | bi | b |
| 3 | tri | t |
| 4 | quad | q |
| 5 | pent | p |
| 6 | hex | h |
| 7 | sept | s |
| 8 | oct | o |
| 9 | enn | e |
💡 Naming Formula: Rootdigit1 + Rootdigit2 + Rootdigit3 + “ium”
Example for Z=120: un + bi + nil + ium = unbinilium (symbol: Ubn)
Example for Z=120: un + bi + nil + ium = unbinilium (symbol: Ubn)
✅ Permanent names honor scientists/places (e.g., Z=106: Seaborgium for Glenn Seaborg). All elements up to Z=118 have official names now!
Electronic Configurations & Periodicity
⚛️ Period number tells you the valence shell (\(n\) value):
- Period 1: Fills 1s orbital (e.g., H: \(1s^1\), He: \(1s^2\))
- Period 2: Fills 2s→2p (e.g., Li: \(1s^22s^1\), Ne: \(1s^22s^22p^6\))
- Period 4: Fills 4s→3d→4p (first transition series!)
- Period 6: Fills 6s→4f→5d→6p (lanthanoids)
🚨 NEET Hotspot: Transition elements appear when filling d-orbitals!
• Period 4: Scandium (Z=21, \(3d^14s^2\)) to Zinc (Z=30, \(3d^{10}4s^2\))
• Period 6: Cerium (Z=58) to Lutetium (Z=71) for 4f-series
• Period 4: Scandium (Z=21, \(3d^14s^2\)) to Zinc (Z=30, \(3d^{10}4s^2\))
• Period 6: Cerium (Z=58) to Lutetium (Z=71) for 4f-series
Key NEET Takeaways
- 📌 Modern Periodic Law is based on atomic number (Z)
- 📌 IUPAC group numbering is 1-18 (forget IA/IIA!)
- 📌 Period number = Highest \(n\) in valence shell
- 📌 Naming of Z>100: Use digit roots (un+bi+nil+ium)
- 📌 d-block starts when filling (n-1)d orbitals, f-block when filling (n-2)f
