Properties of the lanthanides

4f-electron counts, 8-coordinate ionic radii, standard potentials and aqueous colours of Ln³⁺: the radius shrinks smoothly while E°(Ln³⁺/Ln) barely changes.


$\ce{La}$	57	0	116.0	−2.379	—	—	colourless
$\ce{Ce}$	58	1	114.3	−2.336	—	1.72	colourless
$\ce{Pr}$	59	2	112.6	−2.353	−3.10	3.20	green
$\ce{Nd}$	60	3	110.9	−2.323	−2.70	—	lilac
$\ce{Pm}$	61	4	109.3	−2.300	−2.60	—	pink (radioactive)
$\ce{Sm}$	62	5	107.9	−2.304	−1.55	—	pale yellow
$\ce{Eu}$	63	6	106.6	−1.991	−0.36	—	very pale pink
$\ce{Gd}$	64	7	105.3	−2.279	—	—	colourless
$\ce{Tb}$	65	8	104.0	−2.280	—	3.10	very pale pink
$\ce{Dy}$	66	9	102.7	−2.295	−2.60	—	pale yellow
$\ce{Ho}$	67	10	101.5	−2.330	−2.80	—	yellow
$\ce{Er}$	68	11	100.4	−2.331	−3.00	—	rose-pink
$\ce{Tm}$	69	12	99.4	−2.319	−2.20	—	pale green
$\ce{Yb}$	70	13	98.5	−2.190	−1.05	—	colourless (absorbs in the near infrared)
$\ce{Lu}$	71	14	97.7	−2.280	—	—	colourless

Blank cells mean the CRC lists no value for that couple. Y³⁺ (101.9 pm) falls between Dy³⁺ and Ho³⁺.

Sources

R. D. Shannon, Acta Crystallogr. A32, 751 (1976) (ionic radii).
P. Vanýsek, “Electrochemical series”, CRC Handbook of Chemistry and Physics, 91st ed. (2010).
N. N. Greenwood, A. Earnshaw, Chemistry of the Elements, 2nd ed. (1997), ch. 30 (colours).

Used in these lessons

The f-block and beyond