Platinum (Pt): Atomic Structure & Chemical Properties

Atomic Structure

Fundamental Particles

• Atomic Number (Z): 78
• Number of Protons: 78
• Number of Electrons: 78 (in a neutral atom)
• Mass Number (common isotope ¹⁹⁵Pt): 195
• Number of Neutrons (for ¹⁹⁵Pt): 117 (Mass Number - Atomic Number = 195 - 78)

Atomic Size

• Metallic Radius: 139 picometers (pm)

Electronic Configuration & Shell Diagram

Electronic Configuration

• Full Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s¹ 4f¹⁴ 5d⁹
  • (Note: Platinum exhibits an anomalous electronic configuration, promoting one electron from the 6s orbital to the 5d orbital to achieve a more stable d⁹ configuration, similar to copper and gold in their respective groups.)
• Noble Gas Configuration: [Xe] 4f¹⁴ 5d⁹ 6s¹

Shell Diagram Representation

The distribution of electrons in different principal energy shells (K, L, M, N, O, P) is as follows:

• K-shell (n=1): 2 electrons (from 1s²)
• L-shell (n=2): 8 electrons (from 2s² 2p⁶)
• M-shell (n=3): 18 electrons (from 3s² 3p⁶ 3d¹⁰)
• N-shell (n=4): 32 electrons (from 4s² 4p⁶ 4d¹⁰ 4f¹⁴)
• O-shell (n=5): 17 electrons (from 5s² 5p⁶ 5d⁹)
• P-shell (n=6): 1 electron (from 6s¹)

Periodic Trends

Ionization Enthalpy

• First Ionization Enthalpy: 870 kJ/mol
  • (High value due to strong nuclear attraction and high effective nuclear charge.)

Electronegativity

• Pauling Scale: 2.28
  • (Relatively high for a metal, reflecting its tendency to hold onto its electrons.)

Electron Gain Enthalpy

• Electron Gain Enthalpy: -205 kJ/mol
  • (Exothermic process, indicating a tendency to accept an electron, though less readily than non-metals.)

Atomic Radius

• Metallic Radius: 139 picometers (pm)
  • (Relatively small due to the lanthanide contraction, which results in a higher effective nuclear charge.)

Key Physical Properties

Density

• Density (at 20°C): 21.45 g/cm³
  • (One of the densest elements.)

State at STP

• State: Solid

Color

• Color: Silvery-white

Melting Point

• Melting Point: 1768.3 °C (2041.45 K)

Boiling Point

• Boiling Point: 3825 °C (4098 K)