Notes on DNF Block Elements

Introduction

Today's topic: DNF Block and its relevance in Inorganic Chemistry for board exams.
Key areas of focus: electronic configuration, general properties, and position in the periodic table.

S Block: Found on the left side.
P Block: Found on the right side.
D Block: Positioned between S and P Block (Group 3 to Group 12).
F Block: Located at the bottom of the periodic table to maintain noble gas positions (Xe and Rn).

D Block elements are also called transition elements due to their intermediate properties between S and P blocks.
IUPAC Definition: Transition elements have half-filled D orbitals in their neutral state or common oxidation state.
Exceptions: Zinc (Zn), Cadmium (Cd), and Mercury (Hg) are not considered transition elements despite being in the D Block due to fully filled D orbitals.

Four series:
- 3D Series: Scandium (Sc) to Zinc (Zn).
- 4D Series: Yttrium (Y) to Cadmium (Cd).
- 5D Series: Lanthanum (La) to Mercury (Hg).
- 6D Series: Actinium (Ac) to Copernicium (Cn).

Formula: n - 1 d^1 to 10 and n s^1 to 2
Example for Scandium (Sc, Atomic Number 21):
- Electronic Configuration: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1
Example for Zinc (Zn, Atomic Number 30):
- Electronic Configuration: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10}.

Metallic Nature: Transition elements generally exhibit metallic properties:
- Hardness and high tensile strength (ability to withstand tension without breaking).
- Ductility (ability to be drawn into wires).
- Malleability (ability to be hammered into thin sheets).
Electropositivity: Ability to lose electrons and form positive ions.
Conductivity: Good conductors of heat and electricity.
Oxides Formation: React with oxygen to form metal oxides with varying basicity/acidic properties.

Atomic radius generally decreases from left to right across a period due to increased nuclear charge and insufficient shielding from inner electrons.
Lanthanoid Contraction: Atomic radius in 4D and 5D series remains almost the same due to poor shielding effect from the f-block elements (lanthanides).

Definition: The energy required to remove an electron from an atom.
Trends: First ionization energy varies, but second and third usually increase.
Factors Affecting Ionization Energy: Size of the atom and effective nuclear charge influence how tightly electrons are held.
Example: Palladium (Pd) is an exception with electronic configuration 5s^0 4d^{10}.

Most common oxidation state for transition elements is +2.
Scandium can only show +3, and Zinc shows +2 due to electronic configurations.
Transition elements generally exhibit variable oxidation states due to close energy levels of NS and N-1D orbitals.

Important to memorize the 3D series for further studies in coordination compounds.
Encouragement to subscribe to the Vedanta J English Channel for more lectures and study tips.
Good luck with board exam preparations!