Hello everyone. In this video,

we will talk about Radon.

Before talking about the main content,

let's introduce some backgrounds about "Ionizing Radiation".

An atom of an element is composed of protons,

neutrons and electrons.

Both protons and neutrons can be found in the nucleus of the atom.

The atomic number of the element depends on number of protons in its nucleus.

The mass number of element is the sum of

the number of protons and the neutrons in the atom.

Radon, in short, Rn,

is a noble gas, that you can't see, smell or taste.

In the periodic table, the mass number of radon is 222,

meaning that it has 86 protons and 136 neutrons.

We call atoms with the same atomic number, but different mass number as "isotopes".

There are at least 21 known radon isotopes.

Radon 222, Radon 220,

and Radon 219 are the most abundant radon isotopes in nature.

The number 222, 220,

and 219 represent the mass number of the isotopes.

Radon isotopes are radionuclide.

This is because radon isotopes are unstable.

Their nucleus spontaneously disintegrate into the nucleus of different elements.

And this disintegration events are accompanied by the emission of radiation.

As radon undergoes radioactive decay,

the radioactive elements produced are called "radon progeny" or "radon daughters".

As the decay continues,

more radon daughters are produced.

3 emission process will occur during the radioactive decay.

Alpha emission will emit a helium atom; beta emission will emit an electron,

and gamma emission will emit a very high energy photon.

Half life is the amount of time required for half of original radioactive atom to decay.

It is different for different radon isotopes.

For example, considering 3 most common radon isotopes,

half life of Rn-222 is 3.82 days,

but 56 seconds for Rn-220, and 4 seconds for Rn-219.

As an indoor pollutant,

Rn-222 is of primary concern because of its relatively long half life time.

Rn-220 is sometimes an issue.

Rn-219 is rarely a problem due to its very short half life time.

Now, let's take a look at the decay chains of the 3 common radon isotopes.

By looking at these decay chains,

you will have an idea about how radon is produced.

The decay chain of Rn-222 starts from

the primordial radionuclide - Uranium 238 and ends as Lead 210.

The radon daughters of Rn-222 mainly undergo alpha and a beta decay.

The decay chain of Rn-220 starts from

primordial radionuclide Thorium 232 and ends as Lead 208.

The radon daughters of Rn-220 also mainly undergo alpha and beta decay.

The decay chain of Rn-219 starts from

primordial radionuclide Uranium 235 and ends as Lead 207.

The radon daughters of Rn-219 also mainly undergo alpha and beta decay.

To conclude, in this video,

we have introduced the characteristics of

radon and some terms relating to its characteristics.

Finally, we discussed the decay chains for 3 common radon isotopes,

Rn-222, Rn-220 and Rn-219.

2.1 Radon (I) - Introduction to Radon

Introduction to Indoor Air Quality

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