Element: Iridium

General data

Element name	Iridium
Chemical symbol	Ir
Atomic number Z	77
Year discovered	1803
Standard state (25°C)	Solid
Category	Transition metal
Block	d
Atomic mass	192.22
CPK color	#175487

Physical properties

Melting point	2719 K (2446 °C)
Boiling point	4701 K (4428 °C)
Density	22.42 g/cm³

Energy properties

First ionization energy	9.1 eV
Electron affinity	1.565 eV

Atomic structure

Protons	77 (Atomic number)
Neutrons (Ir-193, most abundant isotope)	116
Electrons	77
Electron configuration	[Xe] 6s² 4f¹⁴ 5d⁷
Oxidation states	+4, +3
Electronegativity (Pauling)	2.2
Atomic radius (van der Waals)	202 pm

Ionization energies - NIST ASD (77 states)

State	Charge	Ioniz. energy (eV)	Type
Ir I	0+	8.96702 ± 0.00022	measured
Ir II	1+	17 ± 0.3	semi-empirical
Ir III	2+	28 ± 1.6	calculated
Ir IV	3+	40 ± 1.7	calculated
Ir V	4+	57 ± 1.9	calculated
Ir VI	5+	72 ± 2	calculated
Ir VII	6+	89 ± 2	calculated
Ir VIII	7+	105 ± 2.1	calculated
Ir IX	8+	122.7 ± 0.9	semi-empirical
Ir X	9+	194.8 ± 0.6	semi-empirical
Ir XI	10+	217 ± 11	calculated
Ir XII	11+	240 ± 12	calculated
Ir XIII	12+	264 ± 14	calculated
Ir XIV	13+	303 ± 15	calculated
Ir XV	14+	329 ± 16	calculated
Ir XVI	15+	356 ± 17	calculated
Ir XVII	16+	407 ± 20	calculated
Ir XVIII	17+	445 ± 22	calculated
Ir XIX	18+	472 ± 24	calculated
Ir XX	19+	510 ± 30	calculated
Ir XXI	20+	560 ± 30	calculated
Ir XXII	21+	610 ± 30	calculated
Ir XXIII	22+	670 ± 30	calculated
Ir XXIV	23+	720 ± 40	calculated
Ir XXV	24+	770 ± 40	calculated
Ir XXVI	25+	820 ± 40	calculated
Ir XXVII	26+	870 ± 40	calculated
Ir XXVIII	27+	920 ± 50	calculated
Ir XXIX	28+	980 ± 50	calculated
Ir XXX	29+	1030 ± 50	calculated
Ir XXXI	30+	1080 ± 50	calculated
Ir XXXII	31+	1331 ± 4	calculated
Ir XXXIII	32+	1381 ± 4	calculated
Ir XXXIV	33+	1436 ± 5	calculated
Ir XXXV	34+	1493 ± 5	calculated
Ir XXXVI	35+	1548 ± 5	calculated
Ir XXXVII	36+	1603 ± 5	calculated
Ir XXXVIII	37+	1684 ± 4	calculated
Ir XXXIX	38+	1739 ± 4	calculated
Ir XL	39+	1801 ± 4	calculated
Ir XLI	40+	1857 ± 4	calculated
Ir XLII	41+	2083 ± 4	calculated
Ir XLIII	42+	2139 ± 4	calculated
Ir XLIV	43+	2201 ± 4	calculated
Ir XLV	44+	2258 ± 4	calculated
Ir XLVI	45+	2435 ± 4	calculated
Ir XLVII	46+	2500 ± 4	calculated
Ir XLVIII	47+	2656 ± 4	calculated
Ir XLIX	48+	2720.4 ± 1.4	semi-empirical
Ir L	49+	4540 ± 4	calculated
Ir LI	50+	4668 ± 4	calculated
Ir LII	51+	4806 ± 4	calculated
Ir LIII	52+	4952 ± 4	calculated
Ir LIV	53+	5092 ± 5	calculated
Ir LV	54+	5229 ± 5	calculated
Ir LVI	55+	5466 ± 5	calculated
Ir LVII	56+	5609 ± 5	calculated
Ir LVIII	57+	5765 ± 6	calculated
Ir LIX	58+	5910 ± 6	calculated
Ir LX	59+	6315 ± 7	calculated
Ir LXI	60+	6441 ± 10	calculated
Ir LXII	61+	6580 ± 12	calculated
Ir LXIII	62+	6708 ± 15	calculated
Ir LXIV	63+	7274 ± 19	calculated
Ir LXV	64+	7421 ± 24	calculated
Ir LXVI	65+	7710 ± 30	calculated
Ir LXVII	66+	7850 ± 40	calculated
Ir LXVIII	67+	17040 ± 40	calculated
Ir LXIX	68+	17390 ± 50	calculated
Ir LXX	69+	17770 ± 50	calculated
Ir LXXI	70+	18120 ± 60	calculated
Ir LXXII	71+	20210 ± 60	calculated
Ir LXXIII	72+	20650 ± 70	calculated
Ir LXXIV	73+	21200 ± 90	calculated
Ir LXXV	74+	21556.6 ± 0.24	calculated
Ir LXXVI	75+	86442.44 ± 0.25	calculated
Ir LXXVII	76+	88113.6 ± 1.4	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: Iridium (Ir) — © images-of-elements.com (CC BY 3.0)

Isotopes (42)

A	N	Half-life	Decay
Ir-164	87	unknown	α
Ir-165	88	< 1 μs	α
Ir-166	89	11.7 ms	α
Ir-167	90	30.0 ms	α
Ir-168	91	220 ms	α
Ir-169	92	353 ms	α
Ir-170	93	0.87 s	EC/β⁺
Ir-171	94	3.2 s	EC/β⁺
Ir-172	95	4.4 s	EC/β⁺
Ir-173	96	9.0 s	EC/β⁺
Ir-174	97	7.9 s	EC
Ir-175	98	8.9 s	EC/β⁺
Ir-176	99	8.9 s	EC/β⁺
Ir-177	100	30 s	EC/β⁺
Ir-178	101	12 s	EC/β⁺
Ir-179	102	79 s	EC/β⁺
Ir-180	103	1.5 min	EC/β⁺
Ir-181	104	4.90 min	EC/β⁺
Ir-182	105	15 min	EC/β⁺
Ir-183	106	58 min	EC/β⁺
Ir-184	107	3.09 h	EC/β⁺
Ir-185	108	14.4 h	EC/β⁺
Ir-186	109	16.64 h	EC/β⁺
Ir-187	110	10.5 h	EC/β⁺
Ir-188	111	41.5 h	EC/β⁺
Ir-189	112	13.2 d	EC
Ir-190	113	11.78 d	EC/β⁺
Ir-191	114	stable	-
Ir-192	115	73.826 d	β⁻
Ir-193	116	stable	-
Ir-194	117	19.20 h	β⁻
Ir-195	118	2.29 h	β⁻
Ir-196	119	51.9 s	β⁻
Ir-197	120	5.8 min	β⁻
Ir-198	121	9.1 s	β⁻
Ir-199	122	6 s	β⁻
Ir-200	123	43 s	β⁻
Ir-201	124	21 s	β⁻
Ir-202	125	11 s	β⁻
Ir-203	126	unknown	β⁻
Ir-204	127	unknown	β⁻
Ir-205	128	unknown	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