Germanium (Ge) Revision Guide

Atomic Model Details

Germanium (Ge) is a metalloid element in Group 14 and Period 4 of the periodic table.

• Atomic Number (Z): 32
  • Indicates 32 protons in the nucleus.
  • For a neutral atom, there are also 32 electrons.
• Mass Number (A): The most common isotope is Germanium-74 (⁷⁴Ge).
  • Number of Neutrons: A - Z = 74 - 32 = 42 neutrons (for ⁷⁴Ge).
• Atomic Radius:
  • Covalent Radius: Approximately 122 pm.

Electronic Configuration & Shell Diagram

• Electronic Configuration: [Ar] 3d¹⁰ 4s² 4p²
  • This configuration shows that the outermost shell (valence shell) is the 4th shell, containing 4 electrons (2 in 4s and 2 in 4p orbitals).
  • The 3d subshell is completely filled with 10 electrons.
• Shell-wise Electron Distribution:
  • K-shell (n=1): 2 electrons
  • L-shell (n=2): 8 electrons
  • M-shell (n=3): 18 electrons (2 in 3s, 6 in 3p, 10 in 3d)
  • N-shell (n=4): 4 electrons (2 in 4s, 2 in 4p)
  • Valence Electrons: 4 (These are the electrons primarily involved in chemical bonding).

Periodic Trends

Germanium’s position in Group 14 and Period 4 dictates its periodic properties.

Ionization Enthalpy (IE)

• First Ionization Enthalpy: 762 kJ/mol.
• Trend: As we move down Group 14 from Carbon to Germanium, the ionization enthalpy generally decreases. This is due to the increasing atomic size and the enhanced shielding effect of the inner electrons, which reduces the attraction between the nucleus and the outermost electrons. Germanium’s IE is lower than Silicon’s but higher than Tin’s.

Electronegativity (EN)

• Pauling Scale Electronegativity: 2.01.
• Trend: Electronegativity generally decreases down a group due to increasing atomic size and greater distance between the nucleus and valence electrons. Germanium is less electronegative than Carbon and Silicon.

Electron Gain Enthalpy (EGE)

• Electron Gain Enthalpy: -119 kJ/mol.
• Trend: Electron gain enthalpy values generally become less negative (less exothermic) down a group. This is because the added electron is accommodated in a larger shell, further from the nucleus, experiencing less attraction.

Atomic Radius

• Covalent Radius: 122 pm.
• Trend: Atomic radius increases down a group because new electron shells are added with each successive period, leading to a larger electron cloud. Germanium has a larger atomic radius than Silicon.

Key Physical Properties

• Density: 5.323 g/cm³ (at 25 °C).
• State at Room Temperature: Solid.
• Color: Greyish-white, lustrous. It has a metallic luster but is brittle like a non-metal, characteristic of a metalloid.
• Melting Point (MP): 938.25 °C.
• Boiling Point (BP): 2833 °C.
• Classification: Metalloid. Germanium is a semiconductor, meaning its electrical conductivity is intermediate between that of a conductor and an insulator, and it increases with temperature.