Beta Decay of Potassium-40

40K → 40Ca + e− + ν̄e

Overview

Potassium-40 decays to calcium-40 by beta emission (89.3%) or to argon-40 by electron capture (10.7%). With a half-life of 1.25 billion years, K-40 is the largest source of natural radioactivity in the human body. K-Ar dating is used for rocks millions to billions of years old.

Participants

Role Substance Coefficient State
Reactant Potassium K 1 (s)
Product Calcium Ca 1 (s)

Everyday Example

Every human body contains about 4,400 Bq of K-40 radioactivity from potassium in food, primarily from bananas, potatoes, and meat.

Industrial Importance

K-Ar and Ar-Ar dating are used to date volcanic rocks and establish geological timescales. K-40 is also a background radiation source in radiation detection.

Properties

Type
Nuclear
Reversible
No
Energy
Exothermic
ΔH
-130000000.0 kJ/mol

Related Reactions

Alpha Decay of Polonium-210 Alpha Decay of Radium-226 Alpha Decay of Radon-222 Alpha Decay of Thorium-232 Alpha Decay of Uranium-238 Americium-241 Alpha Decay Beta Decay of Carbon-14 Beta Decay of Cesium-137 Beta Decay of Cobalt-60 Beta Decay of Iodine-131

Frequently Asked Questions

What is the equation for Beta Decay of Potassium-40?
The balanced equation is: ⁴⁰K → ⁴⁰Ca + e⁻ + ν̄ₑ.
What type of reaction is Beta Decay of Potassium-40?
Beta Decay of Potassium-40 is a nuclear reaction.
Is Beta Decay of Potassium-40 exothermic or endothermic?
Beta Decay of Potassium-40 is exothermic (releases energy). The enthalpy change (ΔH) is -130000000.0 kJ/mol.