LANTHANIDES

The Metals

Production of Elemental Metals

La, Ce, Pr, Nd, Gd:

2MCl₃ + 3Ca Æ 2M + 3CaCl₂ (T > 1000 °C)

Tb, Dy, Ho, Er, Tm, Y:

2MF₃ + 3Ca Æ 2M + 3CaF₂ (MCl₃ is too volatile)

Pm:

PmF₃ + 3 Li Æ Pm + 3LiF

Eu, Sm,Yb:

M₂O₃ + 2La Æ 2M + La₂O₃ (MCl₃ reduced to MCl₂ by Ca)

Mischmetall (mixed light Ln) :

electrolysis of fused LnCl₃/NaCl with graphite anode & graphite or steel cathode

Structures of Elemental Metals

Example Structures:-

View using CrystalMaker

Ce, CCP Structure

Gd, HCP Structure

Pr, hc(4H) Structure

Eu, BCC Structure

Properties of the Metals

• Silvery white, but tarnish in air
• Rather soft (later M are harder)
• High mpt & bpt
• Very reactive Ð (I₁ + I₂ + I₃) comparatively low
  • (reactivity ­ as atomic radius ­ )
• + H₂O Æ M₂O₃ or M(OH)₃ & liberates H₂ ~ slowly in cold, rapidly on heating
• + H⁺ (dilute acid) Æ Ln³⁺ & liberates H₂ ~ rapid at room temperature
• burn easily in air ~ slowly in cold , burn at T > 150 °C
  • Æ sesquioxides, M₂O₃

    (but Ce Æ CeO₂) & (Y is passivated below 1000 °C due to its oxide coating)

  • Æ nitrides, MN
• exothermic reaction with H₂ Æ MH_n (n = 2,3, often results in defect states)
• react readily with C, N₂, Si, P, halogens & other non-metals

  form binaries on heating with most non-metals (e.g. LnN, Ln₂S₃, LnB₆, LnC₂, ...)

Uses of Metals

• <1% Mischmetall or Ln silicides improves strength & workability of low alloy steels for plate and pipes {also used in Mg alloys}
• Mischmetall (50% Ce, 25% La, 25% other light lanthanides) is pyrophoric ~ alloyed with 30% Fe it is used in lighter flints