Europium (Eu) Revision Guide

Atomic Model Details

Europium (Eu) is a rare-earth metal, classified as a lanthanide. Its atomic structure is characterized by the following:

Fundamental Particles

Atomic Symbol: Eu
Atomic Number (Z): 63 (Number of protons)
Atomic Mass (A): 151.964 u (average atomic mass)
Protons: 63
Electrons: 63 (in a neutral atom)
Neutrons: Approximately 89 (for the most abundant isotope, $^{152}\text{Eu}$)

Atomic Size

Metallic Radius (CN 12): 204 pm

Electronic Configuration & Shell Diagram

Electronic Configuration

Europium’s ground state electronic configuration is: [ \text{[Xe]} , 4\text{f}^7 , 6\text{s}^2 ] This configuration is notable for the half-filled 4f subshell, which imparts special stability and influences its chemical properties.

Shell-wise Electron Distribution

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

K-shell (n=1): 2 electrons ($1\text{s}^2$)
L-shell (n=2): 8 electrons ($2\text{s}^2 , 2\text{p}^6$)
M-shell (n=3): 18 electrons ($3\text{s}^2 , 3\text{p}^6 , 3\text{d}^{10}$)
N-shell (n=4): 25 electrons ($4\text{s}^2 , 4\text{p}^6 , 4\text{d}^{10} , 4\text{f}^7$)
O-shell (n=5): 8 electrons ($5\text{s}^2 , 5\text{p}^6$)
P-shell (n=6): 2 electrons ($6\text{s}^2$)

Periodic Trends

Ionization Enthalpy

Europium exhibits relatively low ionization enthalpies, consistent with its metallic character and tendency to form positive ions. The first ionization enthalpy is notably lower than some neighboring lanthanides due to the stability of the half-filled $4\text{f}^7$ subshell after removal of the $6\text{s}^2$ electrons.

First Ionization Enthalpy ($\Delta_{\text{i}}H_1$): 547 kJ/mol
Second Ionization Enthalpy ($\Delta_{\text{i}}H_2$): 1085 kJ/mol

Electronegativity

Europium is a highly electropositive element, meaning it has a strong tendency to lose electrons.

Pauling Electronegativity: 1.2

Electron Gain Enthalpy

As a highly electropositive metal, Europium has a very low affinity for electrons. Its electron gain enthalpy is expected to be positive, indicating that energy would be required to add an electron to a neutral Europium atom.

Atomic Radius

Metallic Radius (CN 12): 204 pm. Europium has one of the largest metallic radii among the lanthanides, attributed to the preference for a divalent state in the metallic lattice, contributing two electrons to the metallic bond rather than three, leading to weaker metallic bonding and larger atomic size.

Key Physical Properties

Europium is a soft, ductile metal known for its distinctive luminescent properties.

Density (at 25°C): 5.244 g/cm³
Standard State: Solid
Appearance: Silvery-white metal, quickly tarnishes in air.
Melting Point: 822 °C (1095 K)
Boiling Point: 1529 °C (1802 K)