Potassium (K)

Soft silvery metallic element belonging to group 1 of the periodic table (alkali metals). Occurs naturally in seawater and a many minerals. Highly reactive, chemically, it resembles sodium in its behavior and compounds. Discovered by Sir Humphry Davy in 1807.

Atomic Number	19
Atomic Weight	39.0983
Mass Number	39

Group	1
Period	4
Block	s

Protons	19 p⁺
Neutrons	20 n⁰
Electrons	19 e^-

Properties

Energy
Atomic Radius	220 pm 234 pm
Molar Volume	45.3 cm³/mol
Covalent Radius	196 pm 193 pm 207 pm 203 pm
Metallic Radius	203 pm 235 pm
Ionic Radius	137 pm 138 pm 146 pm 151 pm 155 pm 159 pm 164 pm
Crystal Radius	151 pm 152 pm 160 pm 165 pm 169 pm 173 pm 178 pm
Van der Waals Radius	280 pm 275 pm 275 pm 309 pm 381.2 pm
Density	0.89 g/cm³ 828 kg/m³
Proton Affinity
Electron Affinity	0.50147 eV/particle
Ionization Energy	4.34066354 eV/particle 31.625 eV/particle 45.8031 eV/particle 60.917 eV/particle 82.66 eV/particle 99.4 eV/particle 117.56 eV/particle 154.87 eV/particle 175.8174 eV/particle 503.67 eV/particle 565.6 eV/particle 631 eV/particle 714.71 eV/particle 786.26 eV/particle 860.92 eV/particle 967.66 eV/particle 1,034.541 eV/particle 4,610.86998 eV/particle 4,934.0482 eV/particle

Heat of Vaporization	2.33 kJ/mol
Heat of Fusion	102.5 kJ/mol
Heat of Formation	89 kJ/mol
Electrons
Electron Shells	2, 8, 8, 1

Valence Electrons	1

Electron Configuration	[Ar] 4s¹

Oxidation States	-1, 1
Electronegativity	4.34 eV/particle 0.0981896 0.82
Electrophilicity	0.7633848415985606 eV/particle
Phases
Phase	Solid
Gas Phase
Boiling Point	1,032.15 K
Melting Point	336.65 K
Critical Pressure	16 MPa
Critical Temperature	2,223.15 K
Triple Point
Visual
Color	Silver #ff1493 #8f40d4 #8f40d4
Appearance	silvery gray
Refractive Index
Thermodynamic Properties
Thermal Conductivity	79 W/(m K)
Thermal Expansion
Molar Heat Capacity	29.6 J/(mol K)
Specific Heat Capacity	0.757 J/(g⋅K)
Heat Capacity Ratio (Adiabatic Index)
Electrical Properties
Type	Conductor
Electrical Conductivity	14 MS/m
Electrical Resistivity	0.00000007000000000002 m Ω
Superconducting Point
Magnetism
Type	paramagnetic
Magnetic Susceptibility (Mass)	0.0000000067 m³/Kg
Magnetic Susceptibility (Molar)	0.000000000262 m³/mol
Magnetic Susceptibility (Volume)	0.00000574
Magnetic Ordering
Curie Point
Neel Point
Structure
Crystal Structure	Body Centered Cubic (BCC)
Lattice Constant	5.23 Å
Lattice Angles	π/2, π/2, π/2
Mechanical Properties
Hardness	0.363 MPa 0.4 MPa
Bulk Modulus	3.1 GPa
Shear Modulus	1.3 GPa
Young Modulus
Poisson Ratio
Speed of Sound	2,000 m/s
Classification
Category	Alkali metals, Alkali metals
CAS Group	IA
IUPAC Group	IA
Glawe Number	10
Mendeleev Number	3
Pettifor Number	10
Geochemical Class	alkali metal
Goldschmidt Class	litophile
Other
Gas Basicity
Dipole Polarizability	289.7 ± 0.3 a₀
C6 Dispersion Coefficient	3,923 a₀ 3,910 a₀
Allotropes
Neutron Cross Section	2.1
Neutron Mass Absorption	0.0018
Quantum Numbers	2S1/2
Space Group	229 (Im_3m)

Isotopes of Potassium

Stable Isotopes	3
Unstable Isotopes	26
Radioactive Isotopes	24

³¹K

Abundance	Radioactive ☢️
Relative Atomic Mass	31.03678 ± 0.000322 Da
Mass Number	31
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	2019
Parity	+

³¹K Decay Modes

Decay Mode	Intensity
3p	100%

³²K

Abundance
Relative Atomic Mass	32.023607 ± 0.000429 Da
Mass Number	32
G-Factor
Half Life
Spin	1
Quadrupole Moment
Discovery Year
Parity	+

³²K Decay Modes

Decay Mode	Intensity
p (proton emission)	%

³³K

Abundance
Relative Atomic Mass	33.008095 ± 0.000215 Da
Mass Number	33
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year
Parity	+

³³K Decay Modes

Decay Mode	Intensity
p (proton emission)	%

³⁴K

Abundance
Relative Atomic Mass	33.99869 ± 0.00021 Da
Mass Number	34
G-Factor
Half Life
Spin	1
Quadrupole Moment
Discovery Year
Parity	+

³⁴K Decay Modes

Decay Mode	Intensity
p (proton emission)	%

³⁵K

Abundance	Radioactive ☢️
Relative Atomic Mass	34.988005406 ± 0.00000055 Da
Mass Number	35
G-Factor	0.26133333333333 ± 0.0046666666666667
Half Life	175.2 ± 1.9 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1976
Parity	+

³⁵K Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0.37%

³⁶K

Abundance	Radioactive ☢️
Relative Atomic Mass	35.981301887 ± 0.000000349 Da
Mass Number	36
G-Factor	0.274 ± 0.0005
Half Life	341 ± 3 ms
Spin	2
Quadrupole Moment
Discovery Year	1967
Parity	+

³⁶K Decay Modes

Decay Mode	Intensity
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	100%
β⁺ p (β⁺-delayed proton emission)	0.048%
β⁺α (β⁺-delayed α emission)	0.0034%

³⁷K

Abundance	Radioactive ☢️
Relative Atomic Mass	36.97337589 ± 0.0000001 Da
Mass Number	37
G-Factor	0.13547333333333 ± 0.00004
Half Life	1.23651 ± 0.00094 s
Spin	3/2
Quadrupole Moment	0.109 ± 0.004
Discovery Year	1958
Parity	+

³⁷K Decay Modes

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

³⁸K

Abundance	Radioactive ☢️
Relative Atomic Mass	37.969081114 ± 0.000000209 Da
Mass Number	38
G-Factor	0.457 ± 0.002
Half Life	7.651 ± 0.019 m
Spin	3
Quadrupole Moment
Discovery Year	1937
Parity	+

³⁸K Decay Modes

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

³⁹K

Abundance	93.2581 ± 0.0044
Relative Atomic Mass	38.96370648482 ± 0.00000000489 Da
Mass Number	39
G-Factor	0.26098 ± 0.0000053333333333333
Half Life
Spin	3/2
Quadrupole Moment	0.0603 ± 0.0006
Discovery Year	1921
Parity	+

⁴⁰K

Abundance	Radioactive ☢️ 0.0117 ± 0.0001
Relative Atomic Mass	39.963998165 ± 0.00000006 Da
Mass Number	40
G-Factor
Half Life	1.248 ± 0.003 Gy
Spin	4
Quadrupole Moment	-0.075 ± 0.0008
Discovery Year	1935
Parity	-

⁴⁰K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	89.28%
β⁺ (β⁺ decay; β⁺ = ϵ + e⁺)	10.72%

⁴¹K

Abundance	6.7302 ± 0.0044
Relative Atomic Mass	40.96182525611 ± 0.00000000403 Da
Mass Number	41
G-Factor	0.143248 ± 0.0000033333333333333
Half Life
Spin	3/2
Quadrupole Moment	0.0734 ± 0.0007
Discovery Year	1921
Parity	+

⁴²K

Abundance	Radioactive ☢️
Relative Atomic Mass	41.962402305 ± 0.000000113 Da
Mass Number	42
G-Factor	-0.57125 ± 0.0003
Half Life	12.355 ± 0.007 h
Spin	2
Quadrupole Moment
Discovery Year	1935
Parity	-

⁴²K Decay Modes

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

⁴³K

Abundance	Radioactive ☢️
Relative Atomic Mass	42.960734701 ± 0.00000044 Da
Mass Number	43
G-Factor	0.10886666666667 ± 0.00053333333333333
Half Life	22.3 ± 0.1 h
Spin	3/2
Quadrupole Moment
Discovery Year	1949
Parity	+

⁴³K Decay Modes

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

⁴⁴K

Abundance	Radioactive ☢️
Relative Atomic Mass	43.961586984 ± 0.00000045 Da
Mass Number	44
G-Factor	-0.428 ± 0.002
Half Life	22.13 ± 0.19 m
Spin	2
Quadrupole Moment
Discovery Year	1954
Parity	-

⁴⁴K Decay Modes

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

⁴⁵K

Abundance	Radioactive ☢️
Relative Atomic Mass	44.960691491 ± 0.00000056 Da
Mass Number	45
G-Factor	0.1156 ± 0.00053333333333333
Half Life	17.8 ± 0.6 m
Spin	3/2
Quadrupole Moment
Discovery Year	1964
Parity	+

⁴⁵K Decay Modes

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

⁴⁶K

Abundance	Radioactive ☢️
Relative Atomic Mass	45.961981584 ± 0.00000078 Da
Mass Number	46
G-Factor	-0.5255 ± 0.003
Half Life	96.3 ± 0.08 s
Spin	2
Quadrupole Moment
Discovery Year	1965
Parity	-

⁴⁶K Decay Modes

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

⁴⁷K

Abundance	Radioactive ☢️
Relative Atomic Mass	46.961661612 ± 0.0000015 Da
Mass Number	47
G-Factor	3.866 ± 0.018
Half Life	17.38 ± 0.03 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1964
Parity	+

⁴⁷K Decay Modes

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

⁴⁸K

Abundance	Radioactive ☢️
Relative Atomic Mass	47.965341184 ± 0.00000083 Da
Mass Number	48
G-Factor
Half Life	6.83 ± 0.14 s
Spin	1
Quadrupole Moment
Discovery Year	1972
Parity	-

⁴⁸K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	1.14%

⁴⁹K

Abundance	Radioactive ☢️
Relative Atomic Mass	48.968210753 ± 0.00000086 Da
Mass Number	49
G-Factor	2.6772 ± 0.0016
Half Life	1.26 ± 0.05 s
Spin	1/2
Quadrupole Moment	0
Discovery Year	1972
Parity	+

⁴⁹K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	86%

⁵⁰K

Abundance	Radioactive ☢️
Relative Atomic Mass	49.972380015 ± 0.0000083 Da
Mass Number	50
G-Factor	0
Half Life	472 ± 4 ms
Spin	0
Quadrupole Moment	0
Discovery Year	1972
Parity	-

⁵⁰K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	28.6%
2n (2-neutron emission)	%

⁵¹K

Abundance	Radioactive ☢️
Relative Atomic Mass	50.975828664 ± 0.000014 Da
Mass Number	51
G-Factor	0.342 ± 0.0013333333333333
Half Life	365 ± 5 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1983
Parity	+

⁵¹K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	65%
2n (2-neutron emission)	%

⁵²K

Abundance	Radioactive ☢️
Relative Atomic Mass	51.981602 ± 0.000036 Da
Mass Number	52
G-Factor
Half Life	110 ± 4 ms
Spin	2
Quadrupole Moment
Discovery Year	1983
Parity	-

⁵²K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	72.2%
2n (2-neutron emission)	2.3%

⁵³K

Abundance	Radioactive ☢️
Relative Atomic Mass	52.9868 ± 0.00012 Da
Mass Number	53
G-Factor
Half Life	30 ± 5 ms
Spin	3/2
Quadrupole Moment
Discovery Year	1983
Parity	+

⁵³K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	64%
2n (2-neutron emission)	10%

⁵⁴K

Abundance	Radioactive ☢️
Relative Atomic Mass	53.994471 ± 0.000429 Da
Mass Number	54
G-Factor
Half Life	10 ± 5 ms
Spin	2
Quadrupole Moment
Discovery Year	1983
Parity	-

⁵⁴K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	100%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁵K

Abundance	Radioactive ☢️
Relative Atomic Mass	55.000505 ± 0.000537 Da
Mass Number	55
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	2009
Parity	+

⁵⁵K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁶K

Abundance	Radioactive ☢️
Relative Atomic Mass	56.008567 ± 0.000644 Da
Mass Number	56
G-Factor
Half Life
Spin	2
Quadrupole Moment
Discovery Year	2009
Parity	-

⁵⁶K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁷K

Abundance	Radioactive ☢️
Relative Atomic Mass	57.015169 ± 0.000644 Da
Mass Number	57
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	2018
Parity	+

⁵⁷K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁸K

Abundance	Radioactive ☢️
Relative Atomic Mass	58.023543 ± 0.000751 Da
Mass Number	58
G-Factor
Half Life
Spin	2
Quadrupole Moment
Discovery Year	2019
Parity	-

⁵⁸K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

⁵⁹K

Abundance	Radioactive ☢️
Relative Atomic Mass	59.030864 ± 0.000859 Da
Mass Number	59
G-Factor
Half Life
Spin	3/2
Quadrupole Moment
Discovery Year	2018
Parity	+

⁵⁹K Decay Modes

Decay Mode	Intensity
β⁻ (β⁻ decay)	%
β⁻ n (β⁻-delayed neutron emission)	%
2n (2-neutron emission)	%

History

Potassium's symbol K comes from 'kalium' the name of the element in Germany and Scandinavia. Potassium metal was first isolated in 1807 by Sir Humphry Davy, who derived it from caustic potash by the use of electrolysis of the molten salt with the newly discovered voltaic pile. Potassium was the first metal that was isolated by electrolysis. From the English word, potash - pot ashes; Latin kalium, Arab qali, alkali

Discoverers	Sir Humphrey Davy
Discovery Location	England
Discovery Year	1807
Etymology (Name Origin)	English: pot ash; symbol from Latin: kalium, (alkali).
Pronunciation	pe-TASS-i-em (English)

Potassium must be handled with great care with full skin and eye protection

People whose diets are low in potassium can suffer from hypokalemia

Uses

The greatest demand for potash has been in its use for fertilizers. Potassium is an essential constituent for plant growth and is found in most soils. Potassium nitrate is the main explosive ingredient in gunpowder. Potassium hydroxide is used in the manufacture of soft soaps and as an electrolyte in alkaline batteries. Used as potash in making glass & soap. Also as saltpeter, potassium nitrate (KNO3) to make explosives and to color fireworks in mauve. Formerly called kalium (K). Vital to function of nerve and muscle tissures.

Sources

Found in minerals like carnallite [(KMgCl3).6H2O] & sylvite (potassium chloride, KCL). Pure metal is produced by the reaction of hot potassium chloride and sodium vapors in a special retort.

Abundance
Abundance in Earth's crust	20,900 mg/kg
Abundance in Oceans	399 mg/L
Abundance in Human Body	0.2 %
Abundance in Meteor	0.07 %
Abundance in Sun	0.0004 %
Abundance in Universe	0.0003 %

Nuclear Screening Constants

1	s	0.5105
2	p	3.9728
2	s	5.9938
3	p	11.2744
3	s	10.3201
4	s	15.5048

Potassium on ChemicalAid

ATC code	A12BA
Art & Architecture Thesaurus ID	300212821
Australian Educational Vocabulary ID	scot/3560
BNCF Thesaurus ID	22579
Bibliothèque nationale de France ID	121440770
Brockhaus Enzyklopädie online ID	kalium
CAS Registry Number	7440-09-7
ChEBI ID	26216
ChemSpider ID	4575326
DSSTOX compound identifier	DTXCID70820696
DSSTox substance ID	DTXSID9049748
Den Store Danske ID	kalium
DrugBank ID	14500
ECHA Substance Infocard ID	100.028.290
Encyclopedia of China Online Database ID (Second Edition)	211021
Encyclopædia Britannica Online ID	science/potassium
Encyclopædia Universalis ID	potassium
EuroVoc ID	2568
Freebase ID	/m/025s7j4
French Vikidia ID	Potassium
GND ID	4139553-0
Gran Enciclopèdia Catalana ID	0133931
Great Russian Encyclopedia Online ID	2035525
HSDB ID	698
ICSC ID	0716
InChI	InChI=1S/K
InChIKey	ZLMJMSJWJFRBEC-UHFFFAOYSA-N
KBpedia ID	Potassium
KEGG ID	C00238
Latvian National Encyclopedia Online ID	133174
Library of Congress authority ID	sh85105593
MeSH descriptor ID	D011188
NDF-RT ID	N0000146069
NE.se ID	kalium
NKCR AUT ID	ph705338
Namuwiki ID	칼륨
National Diet Library ID	00565080
National Library of Israel J9U ID	987007529540605171
OmegaWiki Defined Meaning	7255
OpenAlex ID	C517785266
Open Food Facts ingredient ID	potassium
PSH ID	5746
PubChem CID	5462222
Quora topic ID	Potassium
RxNorm ID	8588
Spanish Vikidia ID	Potasio
Store medisinske leksikon ID	kalium
Store medisinske leksikon ID	kalium_-_fysiologi
Store norske leksikon ID	kalium
Treccani ID	potassio
UMLS CUI	C0032821
UNII	RWP5GA015D
WordNet 3.1 Synset ID	14674986-n
YSO ID	11555
ZVG number	8150

Potassium (K)

Properties

Isotopes of Potassium

31K

31K Decay Modes

32K

32K Decay Modes

33K

33K Decay Modes

34K

34K Decay Modes

35K

35K Decay Modes

36K

36K Decay Modes

37K

37K Decay Modes

38K

38K Decay Modes

39K

40K

40K Decay Modes

41K

42K

42K Decay Modes

43K

43K Decay Modes

44K

44K Decay Modes

45K

45K Decay Modes

46K

46K Decay Modes

47K

47K Decay Modes

48K

48K Decay Modes

49K

49K Decay Modes

50K

50K Decay Modes

51K

51K Decay Modes

52K

52K Decay Modes

53K

53K Decay Modes

54K

54K Decay Modes

55K

55K Decay Modes

56K

56K Decay Modes

57K

57K Decay Modes

58K

58K Decay Modes

59K

59K Decay Modes