Skip to main content
Hong Kong Observatory Brand Hong Kong - Asia's world city
GovHK Traditional Chinese Simplified Chinese Search
Search Site Map Contact Us
red dot
Print Version
Print Version PDF Version

Exhibit 2
What is Ionizing Radiation?

What is Ionizing Radiation?

The nucleus of the smallest atom - the hydrogen atom, contains one proton only. But those of the larger atoms contain many protons and neutrons. A uranium-238 nucleus contains 92 protons and 146 neutrons.

The nucleus of most atoms is stable, but some nuclei, in particular those larger ones, are unstable.

What is Ionizing Radiation?

An unstable nucleus emits particles and energy. This process is called decay.

These particles or energy are collectively called radiation.

Radiation can be ionizing or non-ionizing. If the energy of radiation is high enough to remove electrons from atoms, thus creating positively charged ions, it is called ionizing radiation.

What is Atom?Exhibit 1
Exhibit 3 What is Non-ionizing Radiation?
Last revision date: <20 Dec 2012>