Why are isotopes radio active?

Answer 1

"By definition, an isotope has unequal amounts of protons and neutrons."

-This is not true.

"Atoms are stable when there are equal amounts of protons and neutrons."

-This is ALSO not true.

For example, Carbon-12 is very stable, and so is Nitrogen-14.

The protons neutrons and electrons in these are:

Carbon-12, ¹²C: 6protons, 6neutrons, 6 electrons

Nitrogen-14 ¹⁴N: 7 protons, 7 neutrons, 7 electrons

These are stable isotopes that have equal amounts of protons and neutrons. They are stable.

Here are some stable isotopes that have unequal amounts of protons and neutrons:

Lithium-7 ⁷Li: 3 protons, 4 neutrons, 3 electrons

Beryllium-9: ⁹Be: 4 protons, 5 neutrons, 4 electrons

So, what makes an isotope stable, and how can you tell?

1. What makes it stable: There is a certain proton to neutron ratio that is stable. Look up "Band of stability" to learn more.
2. How can you tell? Compare the mass of the isotope to the average atomic mass on the periodic table. The further the isotopic mass is from the average atomic mass, the less stable the isotope is.
3. For example. There is an isotope of Hydrogen with a mass of 3 called Tritium, ³H has 1 proton, 2 neutrons, and 1 electron. Since the mass of tritium is 3, which is very far from the average atomic mass of Hydrogen (1.008), tritium is very unlikely to be stable.

Answer 2

Good morning!

Atoms are stable when there are equal amounts of protons and neutrons. By definition, an isotope has unequal amounts of protons and neutrons. This creates an instability in the atom and it decays. However, the way it decays suggests the form of radiation (alpha, beta, gamma).