Actinide
Properties
Actinides have similar properties to lanthanides. The 6d and 7s electronic shells are filled in actinium and thorium, and the 5f shell is being filled with further increase in atomic number; the 4f shell is filled in the lanthanides.

Actinide

Section Title: Properties
Table Section Text: Actinides have similar properties to lanthanides. The 6d and 7s electronic shells are filled in actinium and thorium, and the 5f shell is being filled with further increase in atomic number; the 4f shell is filled in the lanthanides.

Property	Ac	Th	Pa	U	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr

Core charge	89	90	91	92	93	94	95	96	97	98	99	100	101	102	103

atomic mass	[227]	232.0377(4)	231.03588(2)	238.02891(3)	[237]	[244]	[243]	[247]	[247]	[251]	[252]	[257]	[258]	[259]	[266]

Number of natural isotopes	3	7	3	8	3	4	0	0	0	0	0	0	0	0	0

Natural isotopes	225, 227–228	227–232, 234	231, 233–234	233–240	237, 239–240	238–240, 244	—	—	—	—	—	—	—	—	—

Natural quantity isotopes	—	230, 232	231	234, 235, 238	—	—	—	—	—	—	—	—	—	—	—

Longest-lived isotope	227	232	231	238	237	244	243	247	247	251	252	257	258	259	266

Half-life of the longest-lived isotope	21.8 years	14 billion years	32,500 years	4.47 billion years	2.14 million years	80.8 million years	7,370 years	15.6 million years	1,380 years	900 years	1.29 years	100.5 days	52 days	58 min	11 hours

Most common isotope	227	232	231	238	237	239	241	244	249	252	253	255	256	255	260

Half-life of the most common isotope	21.8 years	14 billion years	32,500 years	4.47 billion years	2.14 million years	24,100 years	433 years	18.1 years	320 days	2.64 years	20.47 days	20.07 hours	78 min	3.1 min	2.7 min

Electronic configuration in the ground state (gas phase)	6d17s2	6d27s2	5f26d17s2 or 5f16d27s2	5f36d17s2	5f46d17s2 or 5f57s2	5f67s2	5f77s2	5f76d17s2	5f97s2 or 5f86d17s2	5f107s2	5f117s2	5f127s2	5f137s2	5f147s2	5f147s27p1

Electronic configuration in the ground state (solid phase)	6d17s2	5f0.56d1.57s2	5f1.76d1.37s2	5f2.96d1.17s2	5f46d17s2	5f56d17s2	5f66d17s2	5f76d17s2	5f86d17s2	5f96d17s2	5f117s2	5f127s2	5f137s2	5f147s2	5f146d17s2

Oxidation states	2, 3	2, 3, 4	2, 3, 4, 5	2, 3, 4, 5, 6	3, 4, 5, 6, 7	3, 4, 5, 6, 7	2, 3, 4, 5, 6, 7	2, 3, 4, 6	2, 3, 4	2, 3, 4	2, 3, 4	2, 3	2, 3	2, 3	3

Metallic radius, nm	0.203	0.180	0.162	0.153	0.150	0.162	0.173	0.174	0.170	0.186	0.186	? 0.198	? 0.194	? 0.197	? 0.171

Ionic radius, nm: An4+ An3+	— 0.126	0.114 —	0.104 0.118	0.103 0.118	0.101 0.116	0.100 0.115	0.099 0.114	0.099 0.112	0.097 0.110	0.096 0.109	0.085 0.098	0.084 0.091	0.084 0.090	0.084 0.095	0.083 0.088

Temperature, °C: melting boiling	1050 3198	1842 4788	1568 ? 4027	1132.2 4131	639 ? 4174	639.4 3228	1176 ? 2607	1340 3110	986 2627	900 ? 1470	860 ? 996	1530 —	830 —	830 —	1630 —

Density, g/cm3	10.07	11.78	15.37	19.06	20.45	19.84	11.7	13.51	14.78	15.1	8.84	? 9.7	? 10.3	? 9.9	? 15.6

Standard electrode potential, V: E° (An4+/An0) E° (An3+/An0)	— −2.13	−1.83 —	−1.47 —	−1.38 −1.66	−1.30 −1.79	−1.25 −2.00	−0.90 −2.07	−0.75 −2.06	−0.55 −1.96	−0.59 −1.97	−0.36 −1.98	−0.29 −1.96	— −1.74	— −1.20	— −2.10

Color [M(H2O)n]4+ [M(H2O)n]3+	— Colorless	Colorless Blue	Yellow Dark blue	Green Purple	Yellow-green Purple	Brown Violet	Red Rose	Yellow Colorless	Beige Yellow-green	Green Green	— Pink	— —	— —	— —	— —

Sentence(s)

Three isotopes, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, were found in nature.
Three isotopes, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, were found in nature.

final_sentence: Three isotopes, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, were found in nature.
final_sentence: Three isotopes, ²²⁵Ac, ²²⁷Ac and ²²⁸Ac, were found in nature.