Erbium (Er)

Atomic Model Details

Erbium (Er) is a lanthanide element.

Atomic Number (Z): 68
Atomic Mass (A): 167.259 u
Protons: 68
Electrons: 68 (in a neutral atom)
Neutrons: Approximately 99 (average for natural isotopes; e.g., the most abundant isotope $^\{166\}$Er has 98 neutrons).
Atomic Size:
- Metallic Radius (12-coordinate): 178 pm
- Ionic Radius (Er³⁺): 89 pm

Electronic Configuration: [Xe] 4f¹² 6s²
- This configuration indicates that after the stable noble gas core of Xenon (Xe), there are 12 electrons in the 4f subshell and 2 electrons in the 6s subshell. The 4f electrons are inner-shell electrons and contribute significantly to shielding.
Shell-wise Electron Distribution:
- K-shell (n=1): 2 electrons (1s²)
- L-shell (n=2): 8 electrons (2s² 2p⁶)
- M-shell (n=3): 18 electrons (3s² 3p⁶ 3d¹⁰)
- N-shell (n=4): 30 electrons (4s² 4p⁶ 4d¹⁰ 4f¹²)
- O-shell (n=5): 8 electrons (5s² 5p⁶)
- P-shell (n=6): 2 electrons (6s²)

Erbium, like other lanthanides, exhibits specific trends influenced by the filling of its 4f subshell.

Ionization Enthalpy:
- First Ionization Enthalpy (IE₁): 589.3 kJ/mol
- Second Ionization Enthalpy (IE₂): 1150 kJ/mol
- Third Ionization Enthalpy (IE₃): 2195 kJ/mol
- Trend: Relatively low compared to main group elements, typical for metals. The successive ionization enthalpies increase as electrons are removed from the positively charged ion.
Electronegativity (Pauling Scale): 1.24
- Trend: Low, reflecting its metallic character and tendency to lose electrons rather than gain them.
Electron Gain Enthalpy:
- Not readily available; expected to be positive or near zero, indicating a low tendency to gain electrons due to its metallic character and stable 4f¹² 6s² configuration.
Atomic Radius:
- Metallic radius generally decreases across the lanthanide series (Lanthanoid Contraction) due to poor shielding by the 4f electrons, leading to a stronger attraction between the nucleus and the outer electrons.

Density: 9.066 g/cm³ (at 25 °C)
State: Solid (at 25 °C and 1 atm)
Color: Silvery-white metal with a bright metallic luster. It tarnishes slowly in air.
Melting Point (MP): 1529 °C (1802 K)
Boiling Point (BP): 2868 °C (3141 K)