19 K Potassium 39.098 u

Potassium

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Period
4
Group
1
Block
s-block
Phase (STP)
Solid

Potassium is an essential alkali metal for all living cells. It is the seventh most abundant element in Earth's crust.

Appearance: Silvery-gray

About Potassium

Essential to every living cell, potassium is a soft, silvery alkali metal that reacts vigorously with water. It has atomic number 19 and an atomic mass of 39.098, a notably large atomic radius of 243 pm, and a low melting point of 337 K. Its single valence electron ([Ar] 4s1) is loosely held, giving the low electronegativity of 0.82 and a first ionization energy of just 419 kJ/mol. Humphry Davy first isolated the metal in 1807. Potassium is the seventh most abundant element in Earth's crust, but its reactivity means it never occurs free. It belongs to group 1, period 4.

Physical Properties

Atomic Mass 39.098 u
Density 0.862 g/cm³
Melting Point 63.6 °C
Boiling Point 758.9 °C
Phase at STP Solid
Atomic Radius 243.0 pm

Electronic Properties

Electronegativity 0.82
Ionization Energy 418.8 eV
Electron Affinity 48.4 eV
Valence Electrons 1

Electron Configuration

Configuration [Ar] 4s¹

Electron Shell Configuration

Potassium electron shell configuration K 2e⁻ 8e⁻ 8e⁻ 1e⁻
Electron shell structure of Potassium — electrons per shell.
Shell Electrons
1 (K) 2
2 (L) 8
3 (M) 8
4 (N) 1

Position in Periodic Table

Potassium position in the periodic table K

Discovery

Discovered by: Humphry Davy
Year: 1807

Block & Period

Block

s p d f

Period

1 2 3 4 5 6 7

Periodic Table

Lanthanides Actinides

Reactions Involving K

Lead Iodide Precipitation (Golden Rain)

Pb(NO₃)₂ + 2KI → PbI₂↓ + 2KNO₃

Precipitation

Beta Decay of Potassium-40

⁴⁰K → ⁴⁰Ca + e⁻ + ν̄ₑ

Nuclear

Chlorine Displacing Iodine from Potassium Iodide

Cl₂ + 2KI → 2KCl + I₂

Single Replacement

E2 Elimination (Dehydrohalogenation)

C₂H₅Br + KOH → C₂H₄ + KBr + H₂O

Organic

Formation of Potassium Chloride

2K + Cl₂ → 2KCl

Synthesis
View all 13 reactions →

Compounds Containing Potassium

Potassium Aluminum Sulfate

KAl(SO₄)₂

Potassium Bitartrate

KHC₄H₄O₆

Potassium Carbonate

K₂CO₃

Potassium Chloride

KCl

Potassium Chromate

K₂CrO₄

Potassium Cyanide

KCN

Potassium Dichromate

K₂Cr₂O₇

Potassium Feldspar

KAlSi₃O₈

Potassium Ferricyanide

K₃[Fe(CN)₆]

Potassium Ferrocyanide

K₄[Fe(CN)₆]

Potassium Hydrogen Tartrate

KHC₄H₄O₆

Potassium Hydroxide

KOH

More Alkali Metal

3 Li Lithium 11 Na Sodium 37 Rb Rubidium 55 Cs Cesium 87 Fr Francium

Frequently Asked Questions

What is Potassium?
Potassium (K) is a chemical element with atomic number 19. It is a solid at standard temperature and pressure, classified as a alkali metal.
What are the key properties of Potassium?
Potassium has an atomic mass of 39.098 u, density of 0.862 g/cm³, melting point of 63.6°C, boiling point of 758.9°C.
What is the electron configuration of Potassium?
The electron configuration of Potassium is [Ar] 4s1. It is in the s-block of the periodic table.
Who discovered Potassium?
Potassium was discovered by Humphry Davy in 1807.
What is the electronegativity of Potassium?
Potassium has an electronegativity of 0.82 on the Pauling scale.