Element: Radium

General data

Element name	Radium
Chemical symbol	Ra
Atomic number Z	88
Year discovered	1898
Standard state (25°C)	Solid
Category	Alkaline earth metal
Block	s
Atomic mass	[226]
CPK color	#007D00

Physical properties

Melting point	973 K (700 °C)
Boiling point	1413 K (1140 °C)
Density	5 g/cm³

Energy properties

First ionization energy	5.279 eV
Electron affinity	no data

Atomic structure

Protons	88 (Atomic number)
Neutrons (Ra-226, longest-lived isotope)	138
Electrons	88
Electron configuration	[Rn] 7s²
Oxidation states	+2
Electronegativity (Pauling)	0.9
Atomic radius (van der Waals)	283 pm

Ionization energies - NIST ASD (88 states)

State	Charge	Ioniz. energy (eV)	Type
Ra I	0+	5.2784239 ± 0.0000025	measured
Ra II	1+	10.14718 ± 0.00006	measured
Ra III	2+	31 ± 1.6	calculated
Ra IV	3+	41 ± 1.7	calculated
Ra V	4+	52.9 ± 1.9	calculated
Ra VI	5+	64 ± 2	calculated
Ra VII	6+	82 ± 2	calculated
Ra VIII	7+	97 ± 2.1	calculated
Ra IX	8+	124 ± 2.2	calculated
Ra X	9+	140 ± 2.2	calculated
Ra XI	10+	204.9 ± 2.4	calculated
Ra XII	11+	227 ± 2.5	calculated
Ra XIII	12+	250 ± 3	calculated
Ra XIV	13+	274 ± 3	calculated
Ra XV	14+	299 ± 3	calculated
Ra XVI	15+	324 ± 3	calculated
Ra XVII	16+	356 ± 3	calculated
Ra XVIII	17+	382 ± 3	calculated
Ra XIX	18+	409 ± 3	calculated
Ra XX	19+	435 ± 4	calculated
Ra XXI	20+	570 ± 30	calculated
Ra XXII	21+	600 ± 30	calculated
Ra XXIII	22+	630 ± 30	calculated
Ra XXIV	23+	660 ± 30	calculated
Ra XXV	24+	740 ± 40	calculated
Ra XXVI	25+	770 ± 40	calculated
Ra XXVII	26+	860 ± 40	calculated
Ra XXVIII	27+	900 ± 40	calculated
Ra XXIX	28+	970 ± 50	calculated
Ra XXX	29+	1040 ± 50	calculated
Ra XXXI	30+	1110 ± 60	calculated
Ra XXXII	31+	1180 ± 60	calculated
Ra XXXIII	32+	1250 ± 60	calculated
Ra XXXIV	33+	1320 ± 70	calculated
Ra XXXV	34+	1390 ± 70	calculated
Ra XXXVI	35+	1460 ± 70	calculated
Ra XXXVII	36+	1530 ± 80	calculated
Ra XXXVIII	37+	1610 ± 80	calculated
Ra XXXIX	38+	1680 ± 80	calculated
Ra XL	39+	1750 ± 90	calculated
Ra XLI	40+	1820 ± 90	calculated
Ra XLII	41+	1880 ± 100	calculated
Ra XLIII	42+	2208 ± 4	calculated
Ra XLIV	43+	2271 ± 4	calculated
Ra XLV	44+	2338 ± 4	calculated
Ra XLVI	45+	2409 ± 4	calculated
Ra XLVII	46+	2477 ± 4	calculated
Ra XLVIII	47+	2544 ± 4	calculated
Ra XLIX	48+	2662 ± 4	calculated
Ra L	49+	2731 ± 4	calculated
Ra LI	50+	2806 ± 4	calculated
Ra LII	51+	2876 ± 4	calculated
Ra LIII	52+	3155 ± 4	calculated
Ra LIV	53+	3224 ± 5	calculated
Ra LV	54+	3298 ± 5	calculated
Ra LVI	55+	3368 ± 5	calculated
Ra LVII	56+	3682 ± 5	calculated
Ra LVIII	57+	3762 ± 6	calculated
Ra LIX	58+	3959 ± 6	calculated
Ra LX	59+	4040 ± 4	semi-empirical
Ra LXI	60+	6565 ± 10	calculated
Ra LXII	61+	6718 ± 12	calculated
Ra LXIII	62+	6881 ± 15	calculated
Ra LXIV	63+	7056 ± 19	calculated
Ra LXV	64+	7222 ± 24	calculated
Ra LXVI	65+	7380 ± 30	calculated
Ra LXVII	66+	7720 ± 40	calculated
Ra LXVIII	67+	7890 ± 40	calculated
Ra LXIX	68+	8080 ± 50	calculated
Ra LXX	69+	8250 ± 50	calculated
Ra LXXI	70+	8730 ± 60	calculated
Ra LXXII	71+	8880 ± 60	calculated
Ra LXXIII	72+	9040 ± 70	calculated
Ra LXXIV	73+	9200 ± 90	calculated
Ra LXXV	74+	10190 ± 90	calculated
Ra LXXVI	75+	10360 ± 100	calculated
Ra LXXVII	76+	10720 ± 110	calculated
Ra LXXVIII	77+	10890 ± 120	calculated
Ra LXXIX	78+	22900 ± 120	calculated
Ra LXXX	79+	23300 ± 140	calculated
Ra LXXXI	80+	23750 ± 150	calculated
Ra LXXXII	81+	24160 ± 160	calculated
Ra LXXXIII	82+	27830 ± 170	calculated
Ra LXXXIV	83+	28370 ± 190	calculated
Ra LXXXV	84+	29050 ± 200	calculated
Ra LXXXVI	85+	29479.8 ± 0.5	calculated
Ra LXXXVII	86+	116853.5 ± 0.5	calculated
Ra LXXXVIII	87+	118929.5 ± 1.1	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: Radium (Ra) — © images-of-elements.com (CC BY 3.0)

Isotopes (34)

A	N	Half-life	Decay
Ra-201	113	10 ms	α
Ra-202	114	3.8 ms	α
Ra-203	115	31 ms	α
Ra-204	116	58 ms	α
Ra-205	117	220 ms	α
Ra-206	118	240 ms	α
Ra-207	119	1.4 s	α
Ra-208	120	1.11 s	α
Ra-209	121	4.8 s	α
Ra-210	122	3.9 s	α
Ra-211	123	13 s	α
Ra-212	124	13.0 s	α
Ra-213	125	2.73 min	α
Ra-214	126	2.438 s	α
Ra-215	127	1.68 ms	α
Ra-216	128	172 ns	α
Ra-217	129	1.59 μs	α
Ra-218	130	25.91 μs	α
Ra-219	131	9 ms	α
Ra-220	132	18 ms	α
Ra-221	133	16 s	α
Ra-222	134	33.6 s	α
Ra-223	135	11.4352 d	α
Ra-224	136	3.6313 d	α
Ra-225	137	14.8 d	β⁻
Ra-226	138	1600 a	α
Ra-227	139	42.2 min	β⁻
Ra-228	140	5.75 a	β⁻
Ra-229	141	4.0 min	β⁻
Ra-230	142	93 min	β⁻
Ra-231	143	103.9 s	β⁻
Ra-232	144	4.2 min	β⁻
Ra-233	145	30 s	β⁻
Ra-234	146	30 s	β⁻

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