Electronic Configuration Mnemonics: d-Block & f-Block Elements
1. Outer Transition Elements (d-block)
The general configuration is:
[Noble Gas] (n-1)d¹⁻¹⁰ ns¹⁻²
(where n = principal quantum number)
Mnemonic for Order of Filling (d-block series):
“Sister Dolly Takes Pretty Careful Handling For Cooking Nicely, Using Copper & Zinc.”
(Helps remember the 3d, 4d, and 5d transition series.)
- 3d Series (4th Period):
Sc (21) → Ti (22) → V (23) → Cr (24) → Mn (25) → Fe (26) → Co (27) → Ni (28) → Cu (29) → Zn (30)
(Cr & Cu have exceptions: Cr = [Ar] 3d⁵ 4s¹, Cu = [Ar] 3d¹⁰ 4s¹) - 4d Series (5th Period):
Y (39) → Zr (40) → Nb (41) → Mo (42) → Tc (43) → Ru (44) → Rh (45) → Pd (46) → Ag (47) → Cd (48)
(Mo, Ru, Rh, Pd, Ag have exceptions, e.g., Pd = [Kr] 4d¹⁰ 5s⁰) - 5d Series (6th Period):
La (57), Hf (72) → Ta (73) → W (74) → Re (75) → Os (76) → Ir (77) → Pt (78) → Au (79) → Hg (80)
2. Inner Transition Elements (f-block)
The general configuration is:
[Noble Gas] (n-2)f¹⁻¹⁴ (n-1)d⁰⁻¹ ns²
Mnemonic for Lanthanides (4f Series):
“Ladies Can’t Put Nickels Properly in Slot-machines. Every Girl Tries Daily, However, Every Time You Look.”
(Helps remember the order: La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)
- Lanthanides (4f Series, 6th Period):
La (57) → Ce (58) → Pr (59) → Nd (60) → Pm (61) → Sm (62) → Eu (63) → Gd (64) → Tb (65) → Dy (66) → Ho (67) → Er (68) → Tm (69) → Yb (70) → Lu (71)
Mnemonic for Actinides (5f Series):
“Aunty (Th) Pawns (Pa) Uncle’s (U) Necklace (Np) to Pay (Pu) for America’s (Am) Beautiful (Bk) Cactus (Cf) in Einstein’s (Es) Farm (Fm), Mending (Md) Nothing (No) for Long (Lr).”
(Helps remember the order: Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, Md, No, Lr)
- Actinides (5f Series, 7th Period):
Ac (89) → Th (90) → Pa (91) → U (92) → Np (93) → Pu (94) → Am (95) → Cm (96) → Bk (97) → Cf (98) → Es (99) → Fm (100) → Md (101) → No (102) → Lr (103)
Key Exceptions to Remember:
- Chromium (Cr): [Ar] 3d⁵ 4s¹ (not 3d⁴ 4s²)
- Copper (Cu): [Ar] 3d¹⁰ 4s¹ (not 3d⁹ 4s²)
- Lanthanum (La): [Xe] 5d¹ 6s² (not 4f)
- Gadolinium (Gd): [Xe] 4f⁷ 5d¹ 6s² (half-filled stability)
