Some properties of the rare-earth elements (values recommended by Ames Laboratory) part I

scandium yttrium lanthanum cerium

atomic number 21 39 57 58

atomic weight 44.956 88.905 138.91 140.12

colour of element silvery silvery silvery silvery

melting point (°C)¹ 1,541 1,522 9.21 799

boiling point (°C)² 2,831 3,338 3,457 3,426

density at 25 °C (grams per cubic centimetre) 2.9890 4.4689 6.1453 6.672

conduction electrons in metal 3 3 3 3(3.1)

valence in aqueous solution 3 3 3 3,4

colour in aqueous solution colourless colourless colourless colourless

colour of oxide white white white off-white (dicerium trioxide); cream (cerium dioxide)

heat of fusion (kilocalories per gram atom) 3,369 2,732 1,482 1,238

heat of vaporization² (kilocalories per gram atom) 89.9 101.3 103.1 101.1

electrical resistivity at 25 °C 【ohm-centimetres(10⁻⁶)】 52 59 61–80 70–80

Nèel point (°K) none none none 12.5

Curie point (°K) none none none —

compressibility at 25 °C 【square centimetres per kilogram (10⁻⁶)】 2.26 2.68 4.04 4.10

crystal structure³ hcp hcp d-hcp fcc

radius, metallic (angstroms) 1.640 1.801 1.879 1.820

radius, ionic (angstroms) 0.732

(+3) 0.893

(+3) 1.061

(+3) 1.034

(+4, 0.92)

praseodymium neodymium promethium samarium

atomic number 59 60 61 62

atomic weight 140.907 144.24 (145)⁴ 150.35

colour of element silvery silvery silvery silvery

melting point (°C)¹ 931 1,021 1,168 1,077

boiling point (°C)² 3,512 3,068 2,700 1,791

density at 25 °C

(grams per cubic centimetre) 6.773 7.007 — 7.520

conduction electrons in metal 3 3 3 3

valence in aqueous solution 3 3 3 3,2

colour in aqueous solution green rose colourless yellow

colour of oxide black (hexapraseodymium undecaoxide); green (dipraseodymium trioxide) blue cream

heat of fusion

(kilocalories per gram atom) 1,652 1,705 — 2,061

heat of vaporization²

(kilocalories per gram atom) 85.3 78.5 — 49.2

electrical resistivity at 25 °C 【ohm-centimetres(10⁻⁶)】 68 65 — 91

Nèel point (°K) — 20 — 15

Curie point (°K) — — — —

compressibility at 25 °C

【square centimetres per kilogram (10⁻⁶)】 3.21 3.00 (2.8) 3.34

crystal structure³ d-hcp hcp/bcc — rhomb

radius, metallic (angstroms) 1.828 1.821 — 1.804

radius, ionic (angstroms) 1.013

(+4, 0.90) 0.995

(+3) 0.979

(+3) 0.964

(+2, 1.11)

¹Corrected for new temperature scale.

²R. Hullgren, R. Orr, and K. Kelley.

³hcp = hexagonal close-packed; fcc = face-centred cubic; rhomb = rhombohedral; bcc = body-centred cubic.

⁴Radioactive isotope separated from fission residues.