Americium (Am)

Radioactive metallic transuranic element, belongs to the actinoids. Ten known isotopes. Am-243 is the most stable isotope, with a half-life of 7.95*10^3 years. Discovered by Glenn T. Seaborg and associates in 1945, it was obtained by bombarding Uranium-238 with alpha particles.

Atomic Number	95
Atomic Weight	243
Mass Number	223

Group
Period	7
Block	f

Protons	95 p⁺
Neutrons	128 n⁰
Electrons	95 e^-

Properties

Energy
Atomic Radius	175 pm 276 pm
Molar Volume	20.8 cm³/mol
Covalent Radius	166 pm 135 pm 180 pm
Metallic Radius
Ionic Radius	121 pm 126 pm 131 pm 97.5 pm 109 pm 85 pm 95 pm 115.7 pm
Crystal Radius	135 pm 140 pm 145 pm 111.5 pm 123 pm 99 pm 109 pm 129.7 pm
Van der Waals Radius	244 pm 338.1 pm
Density	12 g/cm³
Proton Affinity
Electron Affinity
Ionization Energy	5.9738 eV/particle 11.7 eV/particle 21.7 eV/particle 36.8 eV/particle 50 eV/particle 67.9 eV/particle 95 eV/particle 110 eV/particle 126 eV/particle 141 eV/particle 162 eV/particle 184 eV/particle 206 eV/particle 225 eV/particle 242 eV/particle 284 eV/particle 305 eV/particle 424 eV/particle 451 eV/particle 481 eV/particle 511 eV/particle 541 eV/particle 571 eV/particle 616 eV/particle 646 eV/particle 680 eV/particle 711 eV/particle 860 eV/particle 900 eV/particle 940 eV/particle 980 eV/particle 1,090 eV/particle 1,130 eV/particle 1,240 eV/particle 1,280 eV/particle 1,410 eV/particle 1,490 eV/particle 1,570 eV/particle 1,650 eV/particle 1,740 eV/particle 1,820 eV/particle 1,900 eV/particle 1,980 eV/particle 2,070 eV/particle 2,160 eV/particle 2,240 eV/particle 2,320 eV/particle 2,410 eV/particle 2,000 eV/particle 2,874 eV/particle 2,946 eV/particle 3,021 eV/particle 3,101 eV/particle 3,178 eV/particle 3,251 eV/particle 3,402 eV/particle 3,479 eV/particle 3,563 eV/particle 3,641 eV/particle 3,956 eV/particle 4,033 eV/particle 4,115 eV/particle 4,191 eV/particle 4,642 eV/particle 4,733 eV/particle 4,960 eV/particle 5,050 eV/particle 8,040 eV/particle 8,210 eV/particle 8,400 eV/particle 8,590 eV/particle 8,770 eV/particle 8,950 eV/particle 9,380 eV/particle 9,560 eV/particle 9,770 eV/particle 9,960 eV/particle 10,490 eV/particle 10,650 eV/particle 10,830 eV/particle 11,000 eV/particle 12,400 eV/particle 12,600 eV/particle 13,000 eV/particle 13,190 eV/particle 27,110 eV/particle 27,550 eV/particle 28,040 eV/particle 28,500 eV/particle 33,700 eV/particle 34,300 eV/particle 35,100 eV/particle 35,549.4 eV/particle 139,769.5 eV/particle 142,161 eV/particle

Heat of Vaporization	238.5 kJ/mol
Heat of Fusion	10 kJ/mol
Heat of Formation	284 kJ/mol
Electrons
Electron Shells	2, 8, 18, 32, 25, 8, 2

Valence Electrons	2

Electron Configuration	[Rn] 5f⁷ 7s²

Oxidation States	2, 3, 4, 5, 6, 7
Electronegativity	0.17194
Electrophilicity
Phases
Phase	Solid
Gas Phase
Boiling Point
Melting Point	1,449.15 K
Critical Pressure
Critical Temperature
Triple Point
Visual
Color	Silver #ffffff #545cf2 #545cf2
Appearance	silvery white
Refractive Index
Thermodynamic Properties
Thermal Conductivity
Thermal Expansion
Molar Heat Capacity
Specific Heat Capacity
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type
Electrical Conductivity
Electrical Resistivity
Superconducting Point	0.6 K
Magnetism
Type	paramagnetic
Magnetic Susceptibility (Mass)	0.0000000515 m³/Kg
Magnetic Susceptibility (Molar)	0.00000001251 m³/mol
Magnetic Susceptibility (Volume)	0.000704
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure	Simple Hexagonal ()
Lattice Constant
Lattice Angles	π/2, π/2, 2 π/3
Mechanical Properties
Hardness
Bulk Modulus
Shear Modulus
Young Modulus
Poisson Ratio
Speed of Sound
Classification
Category	Actinides, Actinides
CAS Group
IUPAC Group
Glawe Number	39
Mendeleev Number	26
Pettifor Number	42
Geochemical Class
Goldschmidt Class	synthetic
Other
Gas Basicity
Dipole Polarizability	131 ± 25 a₀
C6 Dispersion Coefficient
Allotropes
Neutron Cross Section	74
Neutron Mass Absorption
Quantum Numbers	8S7/2
Space Group	194 (P63/mmc)

Isotopes of Americium

Stable Isotopes	0
Unstable Isotopes	27
Radioactive Isotopes	27

²²³Am

Abundance	Radioactive ☢️
Relative Atomic Mass	223.04584 ± 0.000322 Da
Mass Number	223
G-Factor
Half Life	10 ± 9 ms
Spin	9/2
Quadrupole Moment
Discovery Year	2015
Parity	-

²²³Am Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²²⁴Am

Abundance	Radioactive ☢️
Relative Atomic Mass	224.046442 ± 0.000429 Da
Mass Number	224
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year
Parity

²²⁴Am Decay Modes

Decay Mode	Intensity
α (α emission)	%
SF (spontaneous fission)	%

²²⁵Am

Abundance	Radioactive ☢️
Relative Atomic Mass	225.045508 ± 0.000429 Da
Mass Number	225
G-Factor
Half Life
Spin	9/2
Quadrupole Moment
Discovery Year
Parity	-

²²⁵Am Decay Modes

Decay Mode	Intensity
α (α emission)	%
SF (spontaneous fission)	%

²²⁶Am

Abundance	Radioactive ☢️
Relative Atomic Mass	226.04613 ± 0.000322 Da
Mass Number	226
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year
Parity

²²⁶Am Decay Modes

Decay Mode	Intensity
α (α emission)	%
SF (spontaneous fission)	%

²²⁷Am

Abundance	Radioactive ☢️
Relative Atomic Mass	227.045282 ± 0.000215 Da
Mass Number	227
G-Factor
Half Life
Spin	9/2
Quadrupole Moment
Discovery Year
Parity	-

²²⁷Am Decay Modes

Decay Mode	Intensity
α (α emission)	%
SF (spontaneous fission)	%

²²⁸Am

Abundance	Radioactive ☢️
Relative Atomic Mass	228.046001 ± 0.000215 Da
Mass Number	228
G-Factor
Half Life
Spin
Quadrupole Moment
Discovery Year
Parity

²²⁸Am Decay Modes

Decay Mode	Intensity
α (α emission)	%
SF (spontaneous fission)	%

²²⁹Am

Abundance	Radioactive ☢️
Relative Atomic Mass	229.045282534 ± 0.000114169 Da
Mass Number	229
G-Factor
Half Life	1.8 ± 1.5 s
Spin	5/2
Quadrupole Moment
Discovery Year	2015
Parity	-

²²⁹Am Decay Modes

Decay Mode	Intensity
α (α emission)	100%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%

²³⁰Am

Abundance	Radioactive ☢️
Relative Atomic Mass	230.046025 ± 0.000153 Da
Mass Number	230
G-Factor
Half Life	40 ± 9 s
Spin	1
Quadrupole Moment
Discovery Year	2003
Parity	-

²³⁰Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ SF (β⁺-delayed fission)	30%

²³¹Am

Abundance	Radioactive ☢️
Relative Atomic Mass	231.045529 ± 0.000322 Da
Mass Number	231
G-Factor
Half Life
Spin	5/2
Quadrupole Moment
Discovery Year
Parity	-

²³¹Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%
α (α emission)	%

²³²Am

Abundance	Radioactive ☢️
Relative Atomic Mass	232.046613 ± 0.000322 Da
Mass Number	232
G-Factor
Half Life	1.31 ± 0.04 m
Spin	1
Quadrupole Moment
Discovery Year	1967
Parity	-

²³²Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	97%
α (α emission)	%
β⁺ SF (β⁺-delayed fission)	0.069%

²³³Am

Abundance	Radioactive ☢️
Relative Atomic Mass	233.046468 ± 0.000123 Da
Mass Number	233
G-Factor
Half Life	3.2 ± 0.8 m
Spin	5/2
Quadrupole Moment
Discovery Year	2000
Parity	-

²³³Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	%
α (α emission)	4.5%

²³⁴Am

Abundance	Radioactive ☢️
Relative Atomic Mass	234.047731 ± 0.000172 Da
Mass Number	234
G-Factor	0
Half Life	2.32 ± 0.08 m
Spin	0
Quadrupole Moment	0
Discovery Year	1967
Parity	-

²³⁴Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	0.039%
β⁺ SF (β⁺-delayed fission)	0.0066%

²³⁵Am

Abundance	Radioactive ☢️
Relative Atomic Mass	235.047906478 ± 0.000056661 Da
Mass Number	235
G-Factor
Half Life	10.3 ± 0.6 m
Spin	5/2
Quadrupole Moment
Discovery Year	1996
Parity	-

²³⁵Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	99.6%
α (α emission)	0.4%

²³⁶Am

Abundance	Radioactive ☢️
Relative Atomic Mass	236.049427 ± 0.000127 Da
Mass Number	236
G-Factor
Half Life	3.6 ± 0.1 m
Spin	5
Quadrupole Moment
Discovery Year	1998
Parity	-

²³⁶Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	4%

²³⁷Am

Abundance	Radioactive ☢️
Relative Atomic Mass	237.049995 ± 0.000064 Da
Mass Number	237
G-Factor
Half Life	73.6 ± 0.8 m
Spin	5/2
Quadrupole Moment
Discovery Year	1970
Parity	-

²³⁷Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	99.975%
α (α emission)	0.025%

²³⁸Am

Abundance	Radioactive ☢️
Relative Atomic Mass	238.051982531 ± 0.000063243 Da
Mass Number	238
G-Factor
Half Life	98 ± 3 m
Spin	1
Quadrupole Moment
Discovery Year	1950
Parity	+

²³⁸Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	1%

²³⁹Am

Abundance	Radioactive ☢️
Relative Atomic Mass	239.053022729 ± 0.000002127 Da
Mass Number	239
G-Factor
Half Life	11.9 ± 0.1 h
Spin	5/2
Quadrupole Moment
Discovery Year	1949
Parity	-

²³⁹Am Decay Modes

Decay Mode	Intensity
ϵ (electron capture)	99.99%
α (α emission)	0.01%

²⁴⁰Am

Abundance	Radioactive ☢️
Relative Atomic Mass	240.055298374 ± 0.000014849 Da
Mass Number	240
G-Factor
Half Life	50.8 ± 0.3 h
Spin	3
Quadrupole Moment
Discovery Year	1949
Parity	-

²⁴⁰Am Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
α (α emission)	1.9%

²⁴¹Am

Abundance	Radioactive ☢️
Relative Atomic Mass	241.056827343 ± 0.000001195 Da
Mass Number	241
G-Factor	0.64 ± 0.004
Half Life	432.6 ± 0.6 y
Spin	5/2
Quadrupole Moment	4.34 ± 0.05
Discovery Year	1949
Parity	-

²⁴¹Am Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	3.6%

²⁴²Am

Abundance	Radioactive ☢️
Relative Atomic Mass	242.059547358 ± 0.000001199 Da
Mass Number	242
G-Factor	0.3854 ± 0.0017
Half Life	16.02 ± 0.02 h
Spin	1
Quadrupole Moment	-2.4 ± 0.4
Discovery Year	1949
Parity	-

²⁴²Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	82.7%
ϵ (electron capture)	17.3%

²⁴³Am

Abundance	Radioactive ☢️
Relative Atomic Mass	243.061379889 ± 0.00000149 Da
Mass Number	243
G-Factor	0.608 ± 0.004
Half Life	7.35 ± 0.009 ky
Spin	5/2
Quadrupole Moment	4.32 ± 0.06
Discovery Year	1950
Parity	-

²⁴³Am Decay Modes

Decay Mode	Intensity
α (α emission)	100%
SF (spontaneous fission)	3.7%

²⁴⁴Am

Abundance	Radioactive ☢️
Relative Atomic Mass	244.064282892 ± 0.0000016 Da
Mass Number	244
G-Factor
Half Life	10.01 ± 0.03 h
Spin	6
Quadrupole Moment
Discovery Year	1950
Parity	-

²⁴⁴Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁵Am

Abundance	Radioactive ☢️
Relative Atomic Mass	245.066452827 ± 0.000002024 Da
Mass Number	245
G-Factor
Half Life	2.05 ± 0.01 h
Spin	5/2
Quadrupole Moment
Discovery Year	1955
Parity	+

²⁴⁵Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁶Am

Abundance	Radioactive ☢️
Relative Atomic Mass	246.069774 ± 0.000019 Da
Mass Number	246
G-Factor
Half Life	39 ± 3 m
Spin	7
Quadrupole Moment
Discovery Year	1955
Parity	-

²⁴⁶Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁷Am

Abundance	Radioactive ☢️
Relative Atomic Mass	247.072092 ± 0.000107 Da
Mass Number	247
G-Factor
Half Life	23 ± 1.3 m
Spin	5/2
Quadrupole Moment
Discovery Year	1967
Parity

²⁴⁷Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%

²⁴⁸Am

Abundance	Radioactive ☢️
Relative Atomic Mass	248.075752 ± 0.000215 Da
Mass Number	248
G-Factor
Half Life
Spin	3
Quadrupole Moment
Discovery Year
Parity	+

²⁴⁸Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

²⁴⁹Am

Abundance	Radioactive ☢️
Relative Atomic Mass	249.07848 ± 0.00032 Da
Mass Number	249
G-Factor
Half Life
Spin	5/2
Quadrupole Moment
Discovery Year
Parity

²⁴⁹Am Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%

History

Americium-241 was first identified in 1944 by Glenn T. Seaborg, Ralph A. James, Leon O. Morgan and Albert Ghiorso at the metallurgical laboratory at the University of Chicago. It was produced by irradiating plutonium with neutrons during the Manhattan Project. Americium was first isolated as a pure compound by Burris Cunningham in 1945, at the University of Chicago. Named after America

Discoverers	G.T.Seaborg, R.A.James, L.O.Morgan, A.Ghiorso
Discovery Location	United States
Discovery Year	1945
Etymology (Name Origin)	Named for the American continent, by analogy with europium.
Pronunciation	am-er-ISH-i-em (English)

Americium is harmful due to its radioactivity

Americium often enters landfills from discarded smoke detectors

Uses

Americium is used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. It is also used as a target material in nuclear research to make even heavier elements. Americium-241 is currently used in smoke detectors.

Sources

Produced by bombarding plutonium with neutrons.

Abundance
Abundance in Earth's crust
Abundance in Oceans
Abundance in Human Body	0 %
Abundance in Meteor	0 %
Abundance in Sun	0 %
Abundance in Universe	0 %

Nuclear Screening Constants

Americium on ChemicalAid

Australian Educational Vocabulary ID	scot/1091
CAB ID	7535
CAS Registry Number	7440-35-9
ChEBI ID	33389
ChemSpider ID	22405
DSSTOX compound identifier	DTXCID6047658
DSSTox substance ID	DTXSID3064693
Den Store Danske ID	americium
ECHA Substance Infocard ID	100.028.313
Elhuyar ZTH ID	020208
Encyclopedia of China Online Database ID (Second Edition)	220632
Encyclopædia Britannica Online ID	science/americium
Encyclopædia Universalis ID	americium
Freebase ID	/m/027sxty
French Vikidia ID	Américium
GND ID	4191405-3
Great Russian Encyclopedia Online ID	1817972
InChI	InChI=1S/Am
InChIKey	LXQXZNRPTYVCNG-UHFFFAOYSA-N
KBpedia ID	Americium
Library of Congress authority ID	sh85004443
MeSH descriptor ID	D000576
National Diet Library ID	00575178
National Library of Israel J9U ID	987007294067605171
OmegaWiki Defined Meaning	155847
OpenAlex ID	C552554468
PDB ligand ID	AM
PDB structure ID	4ZHG
PubChem CID	23966
Römpp online ID	RD-01-01920
Store norske leksikon ID	americium
Treccani ID	americio
UNII	VW92PHU2UY
WordNet 3.1 Synset ID	14652672-n

Americium (Am)

Properties

Isotopes of Americium

223Am

223Am Decay Modes

224Am

224Am Decay Modes

225Am

225Am Decay Modes

226Am

226Am Decay Modes

227Am

227Am Decay Modes

228Am

228Am Decay Modes

229Am

229Am Decay Modes

230Am

230Am Decay Modes

231Am

231Am Decay Modes

232Am

232Am Decay Modes

233Am

233Am Decay Modes

234Am

234Am Decay Modes

235Am

235Am Decay Modes

236Am

236Am Decay Modes

237Am

237Am Decay Modes

238Am

238Am Decay Modes

239Am

239Am Decay Modes

240Am

240Am Decay Modes

241Am

241Am Decay Modes

242Am

242Am Decay Modes

243Am

243Am Decay Modes

244Am

244Am Decay Modes

245Am

245Am Decay Modes

246Am

246Am Decay Modes

247Am

247Am Decay Modes

248Am

248Am Decay Modes

249Am

249Am Decay Modes