Second Row d-Block (4d Series) — Periodic Table Mnemonic
Target: mnemonic for 4d transition metals second row d block
Why is this hard to memorize?
The 4d series — Yttrium through Cadmium — is less commonly tested than 3d but appears in JEE Advanced questions on comparative chemistry and periodic trends across d-block periods. You need to know that 4d elements have higher enthalpies of atomization, greater tendency to form multiple bonds (Mo=Mo), and more stable higher oxidation states compared to their 3d congeners. Exceptions in electronic configuration (Mo and Ag mirror Cr and Cu) and the role of Pd, Rh, and Ru as catalysts are important JEE topics.
Classic mnemonics you should know
"Y Zr Nb Mo Tc Ru Rh Pd Ag Cd — "Yaar Zara Note More Techno Routine Rakh Pad Agr Cd""
Y(Yaar) → Yttrium, Zr(Zara) → Zirconium, Nb(Note) → Niobium, Mo(More) → Molybdenum, Tc(Techno) → Technetium, Ru(Routine) → Ruthenium, Rh(Rakh) → Rhodium, Pd(Pad) → Palladium, Ag(Agr) → Silver, Cd(Cd) → Cadmium.
"Young Zebras Need More Tacos, Running Rhinos Prefer Aged Cheddar"
Y(Young) → Yttrium, Zr(Zebras) → Zirconium, Nb(Need) → Niobium, Mo(More) → Molybdenum, Tc(Tacos) → Technetium, Ru(Running) → Ruthenium, Rh(Rhinos) → Rhodium, Pd(Prefer) → Palladium, Ag(Aged) → Silver, Cd(Cheddar) → Cadmium.
"Y-Zr | Nb-Mo-Tc | Ru-Rh-Pd | Ag-Cd"
Group the ten elements into clusters of 2-3-3-2 and chant them rhythmically. This pattern matches the 3d grouping approach.
The complete list
- Yttrium (Y)
- Zirconium (Zr)
- Niobium (Nb)
- Molybdenum (Mo)
- Technetium (Tc)
- Ruthenium (Ru)
- Rhodium (Rh)
- Palladium (Pd)
- Silver (Ag)
- Cadmium (Cd)
Frequently asked questions
Do I need to memorize 4d series elements for NEET?
NEET focuses primarily on 3d series. However, knowing the 4d order helps for comparative questions and NCERT-based reasoning. JEE Advanced definitely tests 4d and 5d series elements.
Why are 4d and 5d elements more stable in higher oxidation states?
Larger atomic size means lower ionization energies for removing electrons beyond +2 or +3, better orbital overlap for multiple bonding, and stronger ligand field stabilization. For example, MoO₃ is stable while CrO₃ is a strong oxidizer.
Which 4d elements have exceptional electronic configurations?
Molybdenum ([Kr]4d⁵5s¹) mirrors Chromium, and Silver ([Kr]4d¹⁰5s¹) mirrors Copper. Palladium is unique: [Kr]4d¹⁰5s⁰ — it has no electrons in the 5s orbital at all.
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