Electron Capture

Definition and Process

Electron capture is a type of nuclear decay in which an unstable nucleus absorbs an inner orbital electron. This process results in the conversion of a proton into a neutron, thereby changing the atomic number of the element. Electron capture is commonly observed in heavier elements and is one of several modes of radioactive decay.

• Key Point 1: Electron capture decreases the atomic number by one but leaves the mass number unchanged.

• Key Point 2: The process is represented by a nuclear equation where an electron (often denoted as e- or β) is absorbed by the nucleus.

• Example: Beta capture in Francium-233:

Writing Nuclear Equations for Electron Capture

Balanced Nuclear Equations

When an element undergoes electron capture, its nuclear equation must be balanced for both mass number and atomic number. The general form is:

Below are examples for specific elements:

Key Points in Nuclear Equations

• Mass Number Conservation: The sum of mass numbers on both sides of the equation remains the same.

• Atomic Number Change: The atomic number of the product is one less than that of the reactant.

• Application: Electron capture is important in medical imaging and radiometric dating.

Additional info: Electron capture is often accompanied by the emission of X-rays as the atom reorganizes its electrons to fill the vacancy left by the captured electron.