Radioactivity: Meaning, Discovery, Units and Applications Explained Simply

Radioactivity is a natural process where certain materials release energy in the form of radiation. You might have heard about it in connection with nuclear energy, medical treatments, or even space science. It plays an important role in both science and daily life applications. This article explains its meaning, units, discovery, and how it works in a simple way.

Table of Contents

• What is Radioactivity?
• Discovery of Radioactivity
• Important Units of Radioactivity
• Important Laws of Radioactivity
• Real-Life Applications of Radioactivity

What is Radioactivity?

Radioactivity is the spontaneous decay of unstable atomic nuclei. This means that an unstable nucleus breaks apart on its own and releases energy along with particles. 

So, in simple words, when an atom cannot hold itself together properly, it releases energy to become stable.

The fact is, this process cannot be controlled by external conditions. It happens naturally.

The fact is, two main forces act inside the nucleus. One is the electrostatic force of repulsion between positively charged particles, and the other is the strong nuclear force that holds the nucleus together.

But why does instability happen?

As the size of the nucleus increases, the number of particles also increases. This makes it harder for the nucleus to remain stable. That is why heavy elements like uranium and plutonium show radioactivity.

When a radioactive atom decays, it forms a new atom called the daughter nucleus, while the original atom is called the parent nucleus.

But the story does not end here. Sometimes, the daughter nucleus is still unstable. In such cases, it continues to decay further.

This process keeps repeating until a completely stable nucleus is formed.

Now, there’s an interesting question that comes into the picture. What are the main types of radioactive emissions?

Common Types of Radioactive Decay

Radioactivity mainly occurs in three forms.

• Alpha decay: In this process, the nucleus emits alpha particles, which are helium nuclei.
  This causes the mass number of the nucleus to decrease by four units.
• Beta decay:  Here, fast-moving electrons are emitted.
  This increases the atomic number of the nucleus by one unit.
• Gamma decay:  In this type, high-energy photons are released.
  There is no change in mass or atomic number, but energy is lost.

Discovery of Radioactivity

Radioactivity was discovered by Henri Becquerel in 1896. He was studying uranium salts and noticed something surprising. They emitted rays even without sunlight.

And you might wonder after knowing this, how it happened?

He placed a uranium compound in a drawer with photographic plates wrapped in black paper. Later, he found that the plates were exposed, even without light. This showed that radiation was coming from the uranium itself.

This discovery led to the idea of radioactive decay.

Later, scientists like Marie Curie and Pierre Curie studied this phenomenon further.

Important Units of Radioactivity

Radioactivity is measured by counting how many atoms decay in one second. Different units have been used for this purpose over time.

Curie (Ci): Curie is a non-SI4 unit of radioactivity.

It was originally based on 1 gram of radium 226.
1 Curie is equal to 3.7 × 10¹⁰ disintegrations per second.

Rutherford (Rd):Rutherford is another older unit used to measure radioactivity.

1 Rutherford is equal to 10⁶ disintegrations per second, which means one million decays per second.

But why is it not commonly used today? Because it has been replaced by a standard SI unit.

Becquerel (Bq): The SI unit of radioactivity is Becquerel (Bq).

1 Becquerel is equal to 1 disintegration per second. This makes it a simple and standard unit used worldwide.

Important Laws of Radioactivity

Let’s first try to understand how radioactive substances behave over time. Radioactivity follows certain important laws that explain how and why atomic nuclei decay.

• Radioactivity is the result of the decay of the nucleus. This means unstable nuclei break down to become more stable.
• The decay rate of a nucleus is independent of temperature and pressure. So, external conditions do not affect how fast a radioactive substance decays.

• Moving ahead, radioactivity follows the law of conservation of charge.
  This means the total electric charge remains the same before and after decay.
• The physical and chemical properties of the daughter nucleus are different from those of the mother nucleus. So, a new element or isotope is formed after decay.
• The emission of energy from radioactivity is always accompanied by alpha, beta, and gamma radiations. These are the different forms in which energy is released.
• Finally, the rate of decay depends on the number of atoms present at that time. This means more atoms will result in a higher rate of decay.

So, in simple words, radioactivity follows fixed natural laws that cannot be changed by external conditions.

Real-Life Applications of Radioactivity

Radioactivity is not just a theory. It has several real-life uses, some of which are very helpful, while others can be dangerous if not handled properly. 

Medical Applications

In medical imaging, radioactive isotopes like Technetium 99m are used as tracers. These help doctors view organs like the heart, lungs, and bones.

In cancer treatment, radiotherapy uses high-energy radiation such as Cobalt 60 to destroy cancer cells while reducing damage to nearby healthy tissues.

Interestingly, iodine-131 is used to treat thyroid disorders like thyroid cancer and hyperthyroidism.

Industrial Applications

Moving ahead, radioactivity also plays a key role in industries.

• Gamma rays are used to sterilise medical equipment like syringes, gloves, and bandages after packaging.
• Radioactive sources are used to measure the thickness of materials such as paper and metal and to detect faults in pipelines and welds.
• Smoke detectors in homes also use Americium 241. It helps detect smoke and triggers alarms for safety.

Scientific and Environmental Applications

Now, there’s an interesting question that comes here. How do scientists study the past?

• Radiometric dating uses Carbon 14 to find the age of ancient materials. Uranium-lead dating helps determine the age of rocks.
• In agriculture, radiation is used to preserve food by killing bacteria and to develop stronger plant varieties.
• Environmental scientists use radioactive tracers to study pollution, track waste movement, and monitor river changes.

Energy Production

Moving further, radioactivity is a major source of energy.

Nuclear power plants use nuclear fission of elements like uranium to generate electricity. This method produces a large amount of energy and is widely used in many countries.

Everyday Uses

Radioactivity is also present in everyday life.

• Smoke detectors use radioactive materials for safety.
• Food irradiation helps prevent spoilage and increases shelf life.
• Certain signs and devices use radioactive materials to glow in the dark.

In this article, we learned that radioactivity is a natural process where unstable atoms release energy. We also studied how it discovered, its types, the unit of radioactivity, and the SI unit of radioactivity. It is an important concept with many real-life applications.