d and f block elements
Unit- 8 The d & f Block Elements
Presented by: Rajesh Kumar G, PGT Chemistry, JNV Kollam, Kerala, Hyderabad Region
d-Block Elements
Introduction
Definition: Elements belonging to groups 3 to 12 of the periodic table.
Electron Configuration: Last electron enters into the penultimate d-orbital.
Position: d-block elements lie between s-block and p-block elements.
Outline
Key Topics:
Transition Series
General Electronic Configuration
General Characteristics:
Melting and Boiling Point
Atomic and Ionic Size
Ionisation Enthalpy
Oxidation State
Reactivity
Magnetic Properties
Standard Electrode Potential
Periodic Table Overview
Notable Groups:
IA: Alkali Metals
IIA: Alkaline Earths
VIIA: Halogens
Noble Gases: Group 18
Transition Metals: Scandium to Zinc and their properties.
Transition Series
Four Transition Series:
1st Transition Series (3d series): Sc to Zn
2nd Transition Series (4d series): Y to Cd
3rd Transition Series (5d series): La, Hf to Hg
4th Transition Series (6d series): Ac, Rf to Cn
Transition Elements
Definition: Elements with partially filled penultimate d-subshell in their ground state or most common oxidation state.
Notable Exceptions: Zn, Cd, and Hg are not considered transition elements.
General Electronic Configuration
Electronic Configuration: (n-1)d^10 ns¹-²
Example (3d Series):
Sc: [Ar] 3d¹ 4s²
Ti: [Ar] 3d² 4s²
Properties of Transition Elements
General Properties
Magnetic Properties: Due to unpaired electrons.
Color: Formation of colored ions.
Complex Formation: Ability to form coordination complexes.
Catalytic Properties: Due to variable oxidation states and d-orbitals.
Size: Trends in atomic and ionic size.
Melting and Boiling Points: D-block elements typically have high melting and boiling points due to strong metallic bonds.
Melting and Boiling Points
General Trends:
High melting and boiling points due to unpaired electrons.
Exception: Zn, Cd, and Hg have low melting points.
Group 6 (Cr, Mo, W) show the highest melting points.
Atomic and Ionic Radii
Decrease in atomic size from left to right in the periodic table.
Notable increase at the end of the series, particularly in 4d and 5d series due to lanthanoid contraction.
Ionisation Enthalpy
Generally increases from left to right.
Weak shielding by 4f electrons in 5d series leads to high ionization enthalpy.
Oxidation States
Vary widely due to small energy differences between (n-1)d and ns subshells.
Maximum oxidation state can reach +7 (shown by Mn).
Reactivity of Transition Elements
Moderately electropositive, not highly reactive due to high heat of sublimation and high ionization enthalpy.
Magnetic Moment
Types:
Paramagnetic: Due to unpaired electrons.
Diamagnetic: No unpaired electrons, repel from magnetic fields.
Magnetic moment calculated using the formula: µ = √[n(n+2)] BM, where n = number of unpaired electrons.
General Properties of d-Block Elements
Formation of complex compounds.
Exhibit catalytic properties.
Form colored compounds due to d-d transitions.
Potassium Dichromate (K2Cr2O7)
Preparation
Process from Chromite ore (FeCr2O4).
Properties
Orange-red crystalline compound, moderately soluble in cold water.
Uses
Primary standard in volumetric analysis, tanning of leather, and photographic processing.
Potassium Permanganate (KMnO4)
Preparation
Derived from pyrolusite ore (MnO2).
Properties
Purple crystalline compound, shows strong oxidizing properties in various media.
Uses
Laboratory oxidizing agent, antiseptic, and reagent in qualitative analysis.
Inner Transition Elements (f-block)
Definition
Include lanthanides and actinides.
Last electron enters pre-penultimate f-subshell.
Physical and Chemical Properties of Lanthanides
Dense metals with high melting points.
Sensitive to oxidation and form basic oxides.
Chemical and Industrial Applications of Actinoids
Used as nuclear reactor fuels (U and Pu), radioactive properties.
Differences Between Lanthanides and Actinoids
Radioactivity: Actinoids are generally more radioactive.
Use of Inner Transition Elements
Widely used in various industrial and chemical applications.