Isotopes are different versions of the same element.

They have the same number of protons but different amounts of neutrons.

Here’s a simple example:

• Carbon-12 (that’s written as $^{12}\text{C}$): This has 6 protons and 6 neutrons.
• Carbon-14 (written as $^{14}\text{C}$): This has 6 protons and 8 neutrons.

Now, the stability of an atom depends on how many neutrons it has compared to protons.

Some isotopes, like Carbon-14, are unstable. This means they can break down over time in a process called radioactive decay.

On the other hand, stable isotopes keep a balance and do not break down.

In fact, about 80% of elements in nature have stable isotopes.