Beta Decay and Characteristics of Beta Particles

Beta Decay

Concept of Beta Decay

Beta decay occurs when an unstable nucleus emits a beta particle. This process is a type of radioactive decay that helps unstable atoms achieve a more stable nuclear configuration.

• Beta particles are high-energy, high-speed electrons (or positrons) emitted by certain types of radioactive nuclei.

• Beta decay usually occurs in nuclei with an excess number of neutrons.

• During beta decay, a neutron is converted into a proton, and an electron (beta particle) is ejected from the nucleus.

General equation for beta decay:

$^A_ZX \rightarrow ^A_{Z+1}Y + ^0_{-1}e$

• n = neutron

• p = proton

• e- = beta particle (electron)

Example: Beta decay of Selenium-81:

$^{81}_{34}Se \rightarrow ^{81}_{35}Br + ^0_{-1}e$

Example: Writing a Balanced Nuclear Reaction

Write a balanced nuclear reaction for beta decay of Iodine-129:

$^{129}_{53}I \rightarrow ^{129}_{54}Xe + ^0_{-1}e$

Characteristics of Beta Particles

Properties and Comparison with Other Types of Radioactivity

Beta particles are smaller and much faster than alpha particles. They have higher velocity and greater penetrating power, but less ionizing power compared to alpha particles.

Particle	Symbol	Charge	Mass	Velocity	Ionizing Power	Penetrating Power	Shielding
Alpha	$^4_2He$	+2	4 amu	Low	Highest	Lowest	Paper, skin
Beta	$^0_{-1}e$	-1	1/1837 amu	Higher	Lower	Higher	Aluminum, plastic
Gamma	$\gamma$	0	0	Speed of light	Lowest	Highest	Lead, thick concrete

Example: Characteristics of Beta Decay

• Beta particles are smaller in size but have higher velocity and greater penetrating power than alpha particles due to their speed.

• During beta decay, a high-energy, high-speed electron is ejected from the nucleus of an unstable atom.

• Beta particles can penetrate paper and skin, but are stopped by materials like plastic or aluminum.

• Beta particles have a mass number of zero and a charge of -1.