Potassium, also known as kalium, is the second least dense metal after lithium. It is a soft solid that has a low melting point and can easily be cut with a knife and is silvery in appearance, yet begins to tarnish toward grey, immediately after being exposed to air.

1807 by Sir Humphrey Davy, England.

DISCOVERY

English, 'potash' and Arabic 'qali' meaning alkali (symbol K from Latin 'kalium').

ETYMOLOGY

Potassium

Element

K

Symbol

19

19 Atomic Number

Atomic Number

Alkali Metal

Classification

7440-09-7

CAS Number

Silver

Elemental Colour

-

Refractive Index

-

Poisson Ratio

45.676 cm³

Molar Volume

363.00k Pa, 3.582'5 Atm

3.582'5 Atm

Brinell Hardness

0.40

0.40 Mohs Hardness

Mohs Hardness

-

Vickers Hardness

2,000 m/s, Mach 5.830'9

2,000 m/s

Speed of Sound

3.10G Pa, 30.594'6k Atm

30.594'6k Atm

Bulk Modulus

1.30G Pa, 12.830'0k Atm

12.830'0k Atm

Shear Modulus

-

Young Modulus

Allotropes

NONE

336.53 K, 63.38 °C

63.38 °C

Melting Point

1,032.15 K, 759.00 °C

759.00 °C

Boiling Point

713.15 K, 440.00 °C

440.00 °C

Automatic Ignition

-

Flashpoint

2,223.00 K, 1,949.85 °C

1,949.85 °C

Critical Temperature

16.00M Pa, 158 Atm

158 Atm

Critical Pressure

100.000'000 W/(m K)

Thermal Conductivity

-

Thermal Expansion

757.00 J/(kg K)

Specific Heat

2.330 kJ/mol

Heat Fusion

76.900 kJ/mol

Heat Vaporisation

182.000 J/(kg K)

Heat Combustion

-

Curie Point

-

Neel Point

-

Adiabatic Index

Solid

Phase

Conductor

Electrical Type

14.00M S/m

Conductivity

70.00n Ω.m

Resistivity

-

Superconducting Point

-

Magnetic Type

0.000'000'006'7

Mass Susceptibility

0.000'000'000'262'00

Molar Susceptibility

0.000'005'740'00

Volume Susceptibility

Material Composition

0.000'3 %

Universe

0.07 %

Meteorites

0.000'4 %

Sun

1.5 %

Earth Crust

0.042 %

Oceans

0.2 %

Humans

39.098'301'1

Atomic Weight

243 pm

Atomic Radius

196 pm

Covalent Radius Single Bond

193 pm

Covalent Radius Double Bond

-

Covalent Radius Triple Bond

275 pm

Van der Waals Radius

[Ar]4s¹

Electron Configuration

Cubic, Body-centred

Crystal Structure

0.856'00 g/cm³

Density as Solid

0.828'00 g/cm³

Density as Liquid

-

Density as Gas

lm_3m

Space Group Name

229

229 Space Group Number

Space Group Number

π/2, π/2 & π/2

Lattice Angles

532.8, 532.8 & 532.8 pm

Lattice Constants

1

1 Valence

Valence

0.82

0.82 Electronegativity

Electronegativity

48.38 kJ/mol

Electron Affinity

Ionisation Energy

Stable

Half Life

Stable

Lifetime

4s¹ = 4, 0, 0, +1/2

Quantum Numbers

1.960'00 b σ_s

Neutron Cross Section

2.100'00 b σ_a

Neutron Mass Absorption

Stable Isotopes

Unstable Isotopes

Isotopes Overview

Isotope	Stability	Symbol	Type	Protons		Neutrons		Spin	Parity	Mass		Abundance		Mass Measure	Mass Excess		Binding Energy		Dipole Moment		Quadrupole Moment		Halflife in Years		Halflife in Seconds		A01 Decay Probability		A01 Decay Mode	A01 Decay Energy		A01 Decay Daughter	A01 Decay Link	A02 Decay Probability		A02 Decay Mode	A02 Decay Energy		A02 Decay Daughter	A02 Decay Link	A03 Decay Probability		A03 Decay Mode	A03 Decay Energy		A03 Decay Daughter	A03 Decay Link	Y01 Decay Product Yield		Y01 Decay Product Nuclide	Y02 Decay Product Yield		Y02 Decay Product Nuclide	Y03 Decay Product Yield		Y03 Decay Product Nuclide	Y04 Decay Product Yield		Y04 Decay Product Nuclide	Y05 Decay Product Yield		Y05 Decay Product Nuclide	Y06 Decay Product Yield		Y06 Decay Product Nuclide	Y07 Decay Product Yield		Y07 Decay Product Nuclide	Y08 Decay Product Yield		Y08 Decay Product Nuclide	Y09 Decay Product Yield		Y09 Decay Product Nuclide	Y10 Decay Product Yield		Y10 Decay Product Nuclide	Y11 Decay Product Yield		Y11 Decay Product Nuclide	Y12 Decay Product Yield		Y12 Decay Product Nuclide
Isotope_019_k_32_u	Unstable	³²K	Fermion	19	p	13	n	1	1	32.021'920'000'0	u	~ 0	%	~ 0	20.418'000'000'0	MeV	6.969'000'000'0	MeV	-		-		?				?	%	p	1,837.000	keV	³¹Ar	³²K > [ ? % , p , 1,837.0 keV ] > ³¹Ar															?	%	³⁰Si	?	%	²⁹Si	?	%	²⁸Si	?	%	³¹P	?	%	²⁶Mg	?	%	²⁷Mg	?	%	²⁷Mg	?	%	²⁷Mg	?	%	²⁷Mg	?	%	²⁷Mg	?	%	²⁷Mg	?	%	²⁷Mg
Isotope_019_k_33_u	Unstable	³³K	Boson	19	p	14	n	3/2	1	33.007'260'000'0	u	~ 0	%	~ 0	6.763'000'000'0	MeV	7.416'000'000'0	MeV	-		-		7.92E-16	year	25.000	nano-seconds ( x⁻⁹ )	?	%	p	1,674.000	keV	³²Ar	³³K > [ ? % , p , 1,674.0 keV ] > ³²Ar															?	%	³²Si	?	%	²⁸Si	?	%	³¹P
Isotope_019_k_34_u	Unstable	³⁴K	Fermion	19	p	15	n	1	1	33.998'410'000'0	u	~ 0	%	~ 0	-1.481'000'000'0	MeV	7.678'000'000'0	MeV	-		-		1.27E-15	year	40.000	nano-seconds ( x⁻⁹ )	?	%	p	614.000	keV	³³Ar	³⁴K > [ ? % , p , 614.0 keV ] > ³³Ar															?	%	³³S	?	%	³²S
Isotope_019_k_35_u	Unstable	³⁵K	Boson	19	p	16	n	3/2	1	34.988'009'692'0	u	~ 0	%	~ 0	-11.168'900'000'0	MeV	7.965'726'000'0	MeV	-		-		5.64E-9	year	178.000	milli-seconds ( x⁻³ )	100.000'000	%	β+	10,856.300	keV	³⁵Ar	³⁵K > [ 100 % , β+ , 10,856.3 keV ] > ³⁵Ar	0.370'000	%	β+p	?	keV	³⁴Cl	³⁵K > [ 0.37 % , β+p , ? keV ] > ³⁴Cl								100.000'000	%	³⁵Cl	0.370'000	%	³⁴S
Isotope_019_k_36_u	Unstable	³⁶K	Fermion	19	p	17	n	2	1	35.981'292'235'0	u	~ 0	%	~ 0	-17.426'171'000'0	MeV	8.142'472'000'0	MeV	0.548'000'000'0	nm	-		1.08E-8	year	342.000	milli-seconds ( x⁻³ )	100.000'000	%	β+	11,783.170	keV	³⁶Ar	³⁶K > [ 100 % , β+ , 11,783.17 keV ] > ³⁶Ar	0.048'000	%	β+p	?	keV	³⁵Cl	³⁶K > [ 0.048 % , β+p , ? keV ] > ³⁵Cl	0.000'034	%	β+α	?	keV	³²S	³⁶K > [ 0.000034 % , β+α , ? keV ] > ³²S	0.004'800	%	³⁵Cl	0.003'400	%	³²S	?	%	³⁶S
Isotope_019_k_37_u	Unstable	³⁷K	Boson	19	p	18	n	3/2	1	36.973'375'889'0	u	~ 0	%	~ 0	-24.800'199'000'0	MeV	8.339'847'000'0	MeV	0.203'210'000'0	nm	-		3.88E-8	year	1.226	seconds ( x⁰ )	100.000'000	%	β+	5,125.260	keV	³⁷Ar	³⁷K > [ 100 % , β+ , 5,125.26 keV ] > ³⁷Ar															100.000'000	%	³⁷Cl
Isotope_019_k_38_u	Unstable	³⁸K	Fermion	19	p	19	n	3	1	37.969'081'184'0	u	~ 0	%	~ 0	-28.800'691'000'0	MeV	8.438'057'000'0	MeV	1.371'000'000'0	nm	-		1.45E-5	year	458.202	seconds ( x⁰ )	100.000'000	%	β+	4,891.660	keV	³⁸Ar	³⁸K > [ 100 % , β+ , 4,891.66 keV ] > ³⁸Ar															100.000'000	%	³⁸Ar
Isotope_019_k_39_s	Stable	³⁹K	Boson	19	p	20	n	3/2	1	38.963'706'679'0	u	93.258'100	%	36.336'812'538'4	-33.807'011'000'0	MeV	8.557'020'000'0	MeV	0.391'466'200'0	nm	0.049'000'000'0	b	-
Isotope_019_k_40_u	Unstable	⁴⁰K	Fermion	19	p	21	n	4	-1	39.963'998'475'0	u	0.011'700	%	0.004'675'787'8	-33.535'205'000'0	MeV	8.538'083'000'0	MeV	-1.298'100'000'0	nm	-0.061'000'000'0	b	1.25E+9	years	39.507	peta-seconds ( x¹⁵ )	89.280'000	%	β-	1,311.070	keV	⁴⁰Ca	⁴⁰K > [ 89.28 % , β- , 1,311.07 keV ] > ⁴⁰Ca	10.720'000	%	β+	482.491	keV	⁴⁰Ar	⁴⁰K > [ 10.72 % , β+ , 482.491 keV ] > ⁴⁰Ar								10.720'000	%	⁴⁰Ar
Isotope_019_k_41_s	Stable	⁴¹K	Boson	19	p	22	n	3/2	1	40.961'825'762'0	u	6.730'200	%	2.756'812'797'4	-35.559'074'000'0	MeV	8.576'061'000'0	MeV	0.214'870'100'0	nm	0.060'000'000'0	b	-
Isotope_019_k_42_u	Unstable	⁴²K	Fermion	19	p	23	n	2	-1	41.962'402'810'0	u	~ 0	%	~ 0	-35.021'556'000'0	MeV	8.551'245'000'0	MeV	-1.142'500'000'0	nm	-		1.41E-3	year	44.496	kilo-seconds ( x³ )	100.000'000	%	β-	3,525.516	keV	⁴²Ca	⁴²K > [ 100 % , β- , 3,525.516 keV ] > ⁴²Ca															100.000'000	%	⁴²Ca
Isotope_019_k_43_u	Unstable	⁴³K	Boson	19	p	24	n	3/2	1	42.960'715'540'0	u	~ 0	%	~ 0	-36.593'239'000'0	MeV	8.576'635'000'0	MeV	0.163'300'000'0	nm	-		2.54E-3	year	80.300	kilo-seconds ( x³ )	100.000'000	%	β-	1,815.400	keV	⁴³Ca	⁴³K > [ 100 % , β- , 1,815.4 keV ] > ⁴³Ca															100.000'000	%	⁴³Ca
Isotope_019_k_44_u	Unstable	⁴⁴K	Fermion	19	p	25	n	2	-1	43.961'556'804'0	u	~ 0	%	~ 0	-35.809'606'000'0	MeV	8.547'340'000'0	MeV	-0.856'000'000'0	nm	-		4.21E-5	year	1.328	kilo-seconds ( x³ )	100.000'000	%	β-	5,658.900	keV	⁴⁴Ca	⁴⁴K > [ 100 % , β- , 5,658.9 keV ] > ⁴⁴Ca															100.000'000	%	⁴⁴Ca
Isotope_019_k_45_u	Unstable	⁴⁵K	Boson	19	p	26	n	3/2	1	44.960'699'493'0	u	~ 0	%	~ 0	-36.608'186'000'0	MeV	8.554'508'000'0	MeV	0.173'400'000'0	nm	-		3.29E-5	year	1.040	kilo-seconds ( x³ )	100.000'000	%	β-	4,203.800	keV	⁴⁵Ca	⁴⁵K > [ 100 % , β- , 4,203.8 keV ] > ⁴⁵Ca															100.000'000	%	⁴⁵Sc
Isotope_019_k_46_u	Unstable	⁴⁶K	Fermion	19	p	27	n	2	-1	45.961'976'864'0	u	~ 0	%	~ 0	-35.418'323'000'0	MeV	8.518'137'000'0	MeV	-1.051'000'000'0	nm	-		3.33E-6	year	105.000	seconds ( x⁰ )	100.000'000	%	β-	7,716.800	keV	⁴⁶Ca	⁴⁶K > [ 100 % , β- , 7,716.8 keV ] > ⁴⁶Ca															100.000'000	%	⁴⁶Ti
Isotope_019_k_47_u	Unstable	⁴⁷K	Boson	19	p	28	n	1/2	1	46.961'678'473'0	u	~ 0	%	~ 0	-35.696'272'000'0	MeV	8.514'544'000'0	MeV	1.933'000'000'0	nm	-		5.55E-7	year	17.500	seconds ( x⁰ )	100.000'000	%	β-	6,643.850	keV	⁴⁷Ca	⁴⁷K > [ 100 % , β- , 6,643.85 keV ] > ⁴⁷Ca															100.000'000	%	⁴⁷Ti
Isotope_019_k_48_u	Unstable	⁴⁸K	Fermion	19	p	29	n	2	-1	47.965'513'535'0	u	~ 0	%	~ 0	-32.123'935'000'0	MeV	8.430'887'000'0	MeV	-		-		2.15E-7	year	6.800	seconds ( x⁰ )	99.000'000	%	β-	12,090.200	keV	⁴⁸Ca	⁴⁸K > [ 99 % , β- , 12,090.2 keV ] > ⁴⁸Ca	1.140'000	%	β-n	2,144.900	keV	⁴⁷Ca	⁴⁸K > [ 1.14 % , β-n , 2,144.9 keV ] > ⁴⁷Ca								1.140'000	%	⁴⁷Ti	?	%	⁴⁸Ti
Isotope_019_k_49_u	Unstable	⁴⁹K	Boson	19	p	30	n	3/2	1	48.967'450'928'0	u	~ 0	%	~ 0	-30.319'265'000'0	MeV	8.386'719'000'0	MeV	-		-		3.99E-8	year	1.260	seconds ( x⁰ )	86.000'000	%	β-n	5,823.500	keV	⁴⁸Ca	⁴⁹K > [ 86 % , β-n , 5,823.5 keV ] > ⁴⁸Ca															?	%	⁴⁸Ti
Isotope_019_k_50_u	Unstable	⁵⁰K	Fermion	19	p	31	n	?	0	49.972'783'355'0	u	~ 0	%	~ 0	-25.352'141'000'0	MeV	8.281'068'000'0	MeV	-		-		1.50E-8	year	472.000	milli-seconds ( x⁻³ )	71.000'000	%	β-	14,219.000	keV	⁵⁰Ca	⁵⁰K > [ 71 % , β- , 14,219.0 keV ] > ⁵⁰Ca	29.000'000	%	β-n	7,866.000	keV	⁴⁹Ca	⁵⁰K > [ 29 % , β-n , 7,866.0 keV ] > ⁴⁹Ca								71.000'000	%	⁵⁰Ti	29.000'000	%	⁴⁹Ti
Isotope_019_k_51_u	Unstable	⁵¹K	Boson	19	p	32	n	3/2	1	50.976'380'000'0	u	~ 0	%	~ 0	-22.002'000'000'0	MeV	8.211'000'000'0	MeV	-		-		1.16E-8	year	365.000	milli-seconds ( x⁻³ )	53.000'000	%	β-	13,861.000	keV	⁵¹Ca	⁵¹K > [ 53 % , β- , 13,861.0 keV ] > ⁵¹Ca	47.000'000	%	β-n	9,498.000	keV	⁵⁰Ca	⁵¹K > [ 47 % , β-n , 9,498.0 keV ] > ⁵⁰Ca								53.000'000	%	⁵¹V	47.000'000	%	⁵⁰Ti
Isotope_019_k_52_u	Unstable	⁵²K	Fermion	19	p	33	n	2	-1	51.982'610'000'0	u	~ 0	%	~ 0	-16.199'000'000'0	MeV	8.097'000'000'0	MeV	-		-		3.33E-9	year	105.000	milli-seconds ( x⁻³ )	64.000'000	%	β-n	11,593.000	keV	⁵¹Ca	⁵²K > [ 64 % , β-n , 11,593.0 keV ] > ⁵¹Ca	21.000'000	%	β-2n	7,229.000	keV	⁵⁰Ca	⁵²K > [ 21 % , β-2n , 7,229.0 keV ] > ⁵⁰Ca								64.000'000	%	⁵¹V	21.000'000	%	⁵⁰Ti
Isotope_019_k_53_u	Unstable	⁵³K	Boson	19	p	34	n	3/2	1	52.987'120'000'0	u	~ 0	%	~ 0	-11.998'000'000'0	MeV	8.017'000'000'0	MeV	-		-		9.51E-10	year	30.000	milli-seconds ( x⁻³ )	67.000'000	%	β-n	12,440.000	keV	⁵²Ca	⁵³K > [ 67 % , β-n , 12,440.0 keV ] > ⁵²Ca	17.000'000	%	β-2n	7,723.000	keV	⁵¹Ca	⁵³K > [ 17 % , β-2n , 7,723.0 keV ] > ⁵¹Ca								65.660'000	%	⁵²Cr	18.400'000	%	⁵¹V	?	%	⁵⁰Ti
Isotope_019_k_54_u	Unstable	⁵⁴K	Fermion	19	p	35	n	2	-1	53.994'200'000'0	u	~ 0	%	~ 0	-5.403'000'000'0	MeV	7.896'000'000'0	MeV	-		-		3.17E-10	year	10.000	milli-seconds ( x⁻³ )	100.000'000	%	β-	18,490.000	keV	⁵⁴Ca	⁵⁴K > [ 100 % , β- , 18,490.0 keV ] > ⁵⁴Ca	?	%	β-n	14,420.000	keV	⁵³Ca	⁵⁴K > [ ? % , β-n , 14,420.0 keV ] > ⁵³Ca								?	%	⁵⁴Cr	?	%	⁵³Cr	?	%	⁵²Cr
Isotope_019_k_55_u	Unstable	⁵⁵K	Boson	19	p	36	n	3/2	1	54.999'710'000'0	u	~ 0	%	~ 0	-0.270'000'000'0	MeV	7.806'000'000'0	MeV	-		-		9.51E-11	year	3.000	milli-seconds ( x⁻³ )	?	%	β-	17,850.000	keV	⁵⁵Ca	⁵⁵K > [ ? % , β- , 17,850.0 keV ] > ⁵⁵Ca	?	%	β-n	15,550.000	keV	⁵⁴Ca	⁵⁵K > [ ? % , β-n , 15,550.0 keV ] > ⁵⁴Ca								?	%	⁵⁵Mn	?	%	⁵⁴Cr	?	%	⁵³Cr	?	%	⁵²Cr	?	%

19 – Potassium, K

19 – Potassium, K

19 – Potassium, K

19 – Potassium, K

19 – Potassium, K

Spectrograph

Elemental Tile

Potassium from Potash

Spectrograph

Elemental Tile

Potassium from Potash

Spectrograph

Elemental Tile

Potassium from Potash

Spectrograph

Elemental Tile

Potassium from Potash

Spectrograph

Elemental Tile

Potassium from Potash