Element: Californium

General data

Element name	Californium
Chemical symbol	Cf
Atomic number Z	98
Year discovered	1950
Standard state (25°C)	Solid
Category	Actinide
Block	f
Atomic mass	[251]
CPK color	#A136D4

Physical properties

Melting point	1173 K (900 °C)
Boiling point	no data
Density	no data

Energy properties

First ionization energy	6.3 eV
Electron affinity	no data

Atomic structure

Protons	98 (Atomic number)
Neutrons (Cf-251, longest-lived isotope)	153
Electrons	98
Electron configuration	[Rn] 7s² 5f¹⁰
Oxidation states	+3
Electronegativity (Pauling)	1.3
Atomic radius (van der Waals)	245 pm

Ionization energies - NIST ASD (98 states)

State	Charge	Ioniz. energy (eV)	Type
Cf I	0+	6.281878 ± 0.000006	measured
Cf II	1+	12 ± 0.4	semi-empirical
Cf III	2+	22.4 ± 0.4	semi-empirical
Cf IV	3+	37.7 ± 0.4	semi-empirical
Cf V	4+	51.9 ± 1.9	calculated
Cf VI	5+	75 ± 2	calculated
Cf VII	6+	91 ± 2	calculated
Cf VIII	7+	112.9 ± 2.1	calculated
Cf IX	8+	133 ± 6	calculated
Cf X	9+	152 ± 7	calculated
Cf XI	10+	178 ± 9	calculated
Cf XII	11+	201 ± 10	calculated
Cf XIII	12+	225 ± 11	calculated
Cf XIV	13+	247 ± 12	calculated
Cf XV	14+	265 ± 14	calculated
Cf XVI	15+	286 ± 15	calculated
Cf XVII	16+	310 ± 15	calculated
Cf XVIII	17+	334 ± 16	calculated
Cf XIX	18+	368 ± 3	calculated
Cf XX	19+	390 ± 4	calculated
Cf XXI	20+	536 ± 4	calculated
Cf XXII	21+	566 ± 4	calculated
Cf XXIII	22+	597 ± 4	calculated
Cf XXIV	23+	630 ± 4	calculated
Cf XXV	24+	662 ± 4	calculated
Cf XXVI	25+	695 ± 4	calculated
Cf XXVII	26+	744 ± 4	calculated
Cf XXVIII	27+	778 ± 4	calculated
Cf XXIX	28+	814 ± 4	calculated
Cf XXX	29+	847 ± 4	calculated
Cf XXXI	30+	1010 ± 50	calculated
Cf XXXII	31+	1050 ± 50	calculated
Cf XXXIII	32+	1090 ± 50	calculated
Cf XXXIV	33+	1120 ± 60	calculated
Cf XXXV	34+	1250 ± 60	calculated
Cf XXXVI	35+	1300 ± 60	calculated
Cf XXXVII	36+	1420 ± 70	calculated
Cf XXXVIII	37+	1470 ± 70	calculated
Cf XXXIX	38+	1620 ± 80	calculated
Cf XL	39+	1700 ± 90	calculated
Cf XLI	40+	1790 ± 90	calculated
Cf XLII	41+	1880 ± 100	calculated
Cf XLIII	42+	1960 ± 100	calculated
Cf XLIV	43+	2050 ± 100	calculated
Cf XLV	44+	2130 ± 110	calculated
Cf XLVI	45+	2220 ± 110	calculated
Cf XLVII	46+	2320 ± 120	calculated
Cf XLVIII	47+	2410 ± 120	calculated
Cf XLIX	48+	2490 ± 120	calculated
Cf L	49+	2580 ± 120	calculated
Cf LI	50+	2670 ± 140	calculated
Cf LII	51+	2750 ± 140	calculated
Cf LIII	52+	3186 ± 4	calculated
Cf LIV	53+	3261 ± 5	calculated
Cf LV	54+	3340 ± 5	calculated
Cf LVI	55+	3424 ± 5	calculated
Cf LVII	56+	3503 ± 5	calculated
Cf LVIII	57+	3581 ± 6	calculated
Cf LIX	58+	3747 ± 6	calculated
Cf LX	59+	3828 ± 7	calculated
Cf LXI	60+	3915 ± 10	calculated
Cf LXII	61+	3998 ± 12	calculated
Cf LXIII	62+	4329 ± 15	calculated
Cf LXIV	63+	4407 ± 19	calculated
Cf LXV	64+	4494 ± 24	calculated
Cf LXVI	65+	4570 ± 30	calculated
Cf LXVII	66+	5100 ± 40	calculated
Cf LXVIII	67+	5190 ± 40	calculated
Cf LXIX	68+	5430 ± 50	calculated
Cf LXX	69+	5520 ± 50	calculated
Cf LXXI	70+	8730 ± 60	calculated
Cf LXXII	71+	8900 ± 60	calculated
Cf LXXIII	72+	9090 ± 70	calculated
Cf LXXIV	73+	9290 ± 90	calculated
Cf LXXV	74+	9480 ± 90	calculated
Cf LXXVI	75+	9660 ± 100	calculated
Cf LXXVII	76+	10140 ± 110	calculated
Cf LXXVIII	77+	10330 ± 120	calculated
Cf LXXIX	78+	10550 ± 120	calculated
Cf LXXX	79+	10740 ± 140	calculated
Cf LXXXI	80+	11300 ± 150	calculated
Cf LXXXII	81+	11470 ± 160	calculated
Cf LXXXIII	82+	11650 ± 170	calculated
Cf LXXXIV	83+	11820 ± 190	calculated
Cf LXXXV	84+	13450 ± 200	calculated
Cf LXXXVI	85+	13660 ± 220	calculated
Cf LXXXVII	86+	14080 ± 240	calculated
Cf LXXXVIII	87+	14280 ± 250	calculated
Cf LXXXIX	88+	29000 ± 300	calculated
Cf XC	89+	29500 ± 300	calculated
Cf XCI	90+	30000 ± 300	calculated
Cf XCII	91+	30500 ± 300	calculated
Cf XCIII	92+	36500 ± 400	calculated
Cf XCIV	93+	37100 ± 400	calculated
Cf XCV	94+	37900 ± 400	calculated
Cf XCVI	95+	38443.5 ± 1	calculated
Cf XCVII	96+	150593 ± 5	calculated
Cf XCVIII	97+	153124 ± 5	calculated

Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.

Photos

Photo of the element: Californium (Cf) — © images-of-elements.com (CC BY 3.0)

Isotopes (20)

A	N	Half-life	Decay
Cf-237	139	0.8 s	α
Cf-238	140	21.1 ms	SF
Cf-239	141	28 s	α
Cf-240	142	41.2 s	α
Cf-241	143	3.8 min	EC/β⁺
Cf-242	144	3.49 min	α
Cf-243	145	10.6 min	EC/β⁺
Cf-244	146	19.4 min	α
Cf-245	147	45.0 min	EC/β⁺
Cf-246	148	35.7 h	α
Cf-247	149	3.11 h	EC
Cf-248	150	334 d	α
Cf-249	151	350.7 a	α
Cf-250	152	13.08 a	α
Cf-251	153	900 a	α
Cf-252	154	2.647 a	α
Cf-253	155	17.78 d	β⁻
Cf-254	156	60.5 d	SF
Cf-255	157	85 min	β⁻
Cf-256	158	12.3 min	SF

Data sources

PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0

More about the data sources