Element: Zirconium

General data

Element name	Zirconium
Chemical symbol	Zr
Atomic number Z	40
Year discovered	1789
Standard state (25°C)	Solid
Category	Transition metal
Block	d
Atomic mass	91.222
CPK color	#94E0E0

Physical properties

Melting point	2128 K (1855 °C)
Boiling point	4682 K (4409 °C)
Density	6.52 g/cm³

Energy properties

First ionization energy	6.634 eV
Electron affinity	0.426 eV

Atomic structure

Protons	40 (Atomic number)
Neutrons (Zr-90, most abundant isotope)	50
Electrons	40
Electron configuration	[Kr] 5s² 4d²
Oxidation states	+4
Electronegativity (Pauling)	1.33
Atomic radius (van der Waals)	186 pm

Ionization energies - NIST ASD (40 states)

State	Charge	Ioniz. energy (eV)	Type
Zr I	0+	6.634126 ± 0.000005	measured
Zr II	1+	13.13	measured
Zr III	2+	23.17 ± 0.004	semi-empirical
Zr IV	3+	34.41836 ± 0.00006	measured
Zr V	4+	80.348 ± 0.007	semi-empirical
Zr VI	5+	96.38 ± 0.04	semi-empirical
Zr VII	6+	112 ± 2	calculated
Zr VIII	7+	133.7 ± 0.5	semi-empirical
Zr IX	8+	153 ± 2.2	calculated
Zr X	9+	172.02 ± 0.05	semi-empirical
Zr XI	10+	214.9 ± 0.4	semi-empirical
Zr XII	11+	236.252 ± 0.025	measured
Zr XIII	12+	426 ± 3	calculated
Zr XIV	13+	470 ± 3	calculated
Zr XV	14+	520 ± 3	calculated
Zr XVI	15+	573 ± 3	calculated
Zr XVII	16+	622 ± 3	calculated
Zr XVIII	17+	690 ± 3	calculated
Zr XIX	18+	745 ± 3	calculated
Zr XX	19+	803 ± 4	calculated
Zr XXI	20+	863 ± 4	calculated
Zr XXII	21+	922 ± 4	calculated
Zr XXIII	22+	1092 ± 3	semi-empirical
Zr XXIV	23+	1144.7 ± 1.2	semi-empirical
Zr XXV	24+	1205.4 ± 1.7	semi-empirical
Zr XXVI	25+	1277 ± 5	semi-empirical
Zr XXVII	26+	1344 ± 3	semi-empirical
Zr XXVIII	27+	1392 ± 7	semi-empirical
Zr XXIX	28+	1525.1 ± 2.2	semi-empirical
Zr XXX	29+	1582.37 ± 0.05	semi-empirical
Zr XXXI	30+	3788 ± 2.1	semi-empirical
Zr XXXII	31+	3950 ± 7	semi-empirical
Zr XXXIII	32+	4127 ± 9	semi-empirical
Zr XXXIV	33+	4300 ± 30	semi-empirical
Zr XXXV	34+	4553 ± 5	semi-empirical
Zr XXXVI	35+	4744 ± 3	semi-empirical
Zr XXXVII	36+	4991 ± 5	semi-empirical
Zr XXXVIII	37+	5146.935 ± 0.014	calculated
Zr XXXIX	38+	21516.471 ± 0.006	calculated
Zr XL	39+	22236.712 ± 0.004	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: Zirconium (Zr) — © images-of-elements.com (CC BY 3.0)

Isotopes (37)

A	N	Half-life	Decay
Zr-77	37	unknown	EC/β⁺
Zr-78	38	unknown	EC/β⁺
Zr-79	39	60 ms	EC/β⁺
Zr-80	40	4.6 s	EC/β⁺
Zr-81	41	5.0 s	EC/β⁺
Zr-82	42	32 s	EC/β⁺
Zr-83	43	41.5 s	EC/β⁺
Zr-84	44	26.0 min	EC/β⁺
Zr-85	45	7.86 min	EC/β⁺
Zr-86	46	16.5 h	EC/β⁺
Zr-87	47	1.68 h	EC/β⁺
Zr-88	48	83.4 d	EC
Zr-89	49	78.364 h	EC/β⁺
Zr-90	50	stable	-
Zr-91	51	stable	-
Zr-92	52	stable	-
Zr-93	53	1.61×10⁶ a	β⁻
Zr-94	54	stable	-
Zr-95	55	64.032 d	β⁻
Zr-96	56	2.29×10¹⁹ a	2β⁻
Zr-97	57	16.749 h	β⁻
Zr-98	58	30.7 s	β⁻
Zr-99	59	2.1 s	β⁻
Zr-100	60	7.1 s	β⁻
Zr-101	61	2.32 s	β⁻
Zr-102	62	2.01 s	β⁻
Zr-103	63	1.38 s	β⁻
Zr-104	64	920 ms	β⁻
Zr-105	65	670 ms	β⁻
Zr-106	66	178 ms	β⁻
Zr-107	67	146 ms	β⁻
Zr-108	68	77.4 ms	β⁻
Zr-109	69	56 ms	β⁻
Zr-110	70	37.6 ms	β⁻
Zr-111	71	24 ms	β⁻
Zr-112	72	30 ms	β⁻
Zr-113	73	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