# Radioactivity and gamma rays

> Unstable nuclei and very penetrating rays


## Objectives

- Describe a radioactive isotope as one with an unstable nucleus that gives out radiation.
- Describe gamma rays as high-energy electromagnetic rays with high penetrating power.
- Explain that an object exposed to gamma rays does not become radioactive.

## 1. Economic importance of the first transition series




## 2. Rays from outside

Predict: what must such a ray be able to do?

- Pass through skin and flesh ✓
- Be attracted by a magnet
- Be visible, like ordinary light

To reach a tumour deep inside the body, the ray must pass through skin and flesh: it needs high penetrating power, as gamma rays have.

[ar-EG] عشان الشعاع يوصل لورم في عمق الجسم، لازم يعدّي من الجلد واللحم: يعني يكون ليه high penetrating power، زي الـ gamma rays.
## 3. Unstable nuclei

Remember: isotopes of an element differ in their numbers of neutrons. Radioactive isotope An isotope with an unstable nucleus that breaks down by itself and gives out radiation. Two isotopes of carbon: only one is radioactive


## 4. Gamma rays

Remember: gamma rays sit at the high-energy end of the electromagnetic spectrum. Many radioactive nuclei give out **gamma rays**. They are electromagnetic rays with very high energy and **high penetrating power**. Gamma rays pass through paper, the body and thin metal; thick lead weakens them a lot


## 5. Exposed is not radioactive

Anything exposed to gamma rays becomes radioactive. Only the source contains the radioactive isotope Contrast: a dental X-ray passes through your teeth. Your teeth do not start giving out rays.


## 6. Check it

Sealed packs of medical gloves are passed near a gamma source to kill germs. Afterwards, the gloves are:

- Radioactive for some time
- Holding gamma rays trapped inside the pack
- Free of germs, and not radioactive ✓

The gamma rays pass through the sealed pack and kill the germs. The gloves take in no radioactive isotope and the rays are not stored, so the gloves give out no radiation afterwards.

[ar-EG] الـ gamma rays بتعدّي من العلبة المقفولة وبتقتل الجراثيم. مفيش radioactive isotope بيدخل الجوانتيات والأشعة مش بتتخزن، فالجوانتيات مش بتطلّع أي radiation بعد كده.
## 7. Summary

A radioactive isotope has an unstable nucleus that gives out radiation. Gamma rays are high-energy electromagnetic rays with high penetrating power. Gamma rays used to treat food or tools do not make them radioactive. Back to the hook: gamma rays can reach a tumour because of their high penetrating power. In Chapter 1: what the gamma rays of cobalt 60 are used for. Can you explain why food treated with gamma rays is safe to eat? Gamma rays used to treat food pass through it and are gone. The food does not become radioactive: only the source contains the radioactive isotope.



Chapter: Transition Elements (https://yaani.ai/en/learn/chemistry/chem-s3-en.ch1)
Source: https://yaani.ai/en/lesson/chem-s3-en.lesson-phys.radioactivity-gamma