Palladium (Pd) Revision Guide

Atomic Model of Palladium (Pd)

Palladium (Pd) is a chemical element with atomic number 46. It belongs to Group 10, Period 5, and the d-block of the periodic table.

Key Atomic Data

• Atomic Number (Z): 46
  • Indicates 46 protons in the nucleus.
  • Indicates 46 electrons in a neutral atom.
• Atomic Mass (Average): 106.42 u (atomic mass units)
• Most Common Isotope: $^{106}\text{Pd}$
• Neutrons (in $^{106}\text{Pd}$): 60 (calculated as Mass Number - Atomic Number = 106 - 46)
• Atomic Radius (Metallic): 137 pm

Electronic Configuration and Shell Diagram

Palladium exhibits an anomalous electronic configuration, where the 5s orbital is completely empty, and the 4d subshell is completely filled.

Electronic Configuration

• Ground State Electronic Configuration: $[\text{Kr}] 4d^{10} 5s^0$
• Orbital-wise Breakdown:
  • K-shell: $1s^2$ (2 electrons)
  • L-shell: $2s^2 2p^6$ (8 electrons)
  • M-shell: $3s^2 3p^6 3d^{10}$ (18 electrons)
  • N-shell: $4s^2 4p^6 4d^{10}$ (18 electrons)
  • O-shell: $5s^0$ (0 electrons)

Shell Diagram Representation (Textual)

A textual representation of electron distribution in shells would be:

• Shell 1 (K): 2 electrons
• Shell 2 (L): 8 electrons
• Shell 3 (M): 18 electrons
• Shell 4 (N): 18 electrons
• Shell 5 (O): 0 electrons This distribution sums to 46 electrons, corresponding to the atomic number of Palladium.

Periodic Trends of Palladium (Pd)

Palladium’s position in the periodic table influences its chemical behavior and properties.

Ionization Enthalpy

• First Ionization Enthalpy: 804.4 kJ/mol
  • This is the energy required to remove the first electron from a neutral gaseous Palladium atom.
• Second Ionization Enthalpy: 1797 kJ/mol
  • This is the energy required to remove the second electron.

Electronegativity

• Pauling Scale Electronegativity: 2.20
  • Palladium has a relatively high electronegativity for a metal, comparable to some non-metals, indicating a strong attraction for electrons in a chemical bond.

Electron Gain Enthalpy

• Electron Gain Enthalpy: -54 kJ/mol
  • This value indicates that energy is released when a neutral gaseous Palladium atom gains an electron, suggesting a slight tendency to accept an electron, though it is not a common behavior for metals.

Atomic Radius

• Metallic Radius: 137 pm
  • This value represents half the distance between the nuclei of two adjacent Palladium atoms in a metallic crystal lattice.
• Ionic Radius (for Pd$^{2+}$): 86 pm
  • The radius of the Pd$^{2+}$ ion is significantly smaller than the neutral atom due to the loss of electrons and increased effective nuclear charge.

Key Physical Properties

Palladium is a precious, silvery-white metal known for its excellent catalytic properties and resistance to corrosion.

Fundamental Physical Properties

• Density (at 20 °C): 12.02 g/cm$^3$
  • Palladium is a dense metal.
• State at Room Temperature (25 °C): Solid
• Color: Silvery-white
  • It possesses a lustrous appearance.
• Melting Point: 1554.9 °C (1828.05 K)
  • Palladium has a relatively high melting point among metals.
• Boiling Point: 2963 °C (3236 K)
  • It has a very high boiling point.