Why are some isotopes considered radioactive?

Answer 1

In an analogy, think of a baby's building blocks. Stock the blocks one on top of another. Eventually the tower of blocks becomes unstable and fall over. Radio-activity can be thought of in the same way. Protons( & Neutrons) stacked 'one on top of another'' become unstable when there are too many of them, hence the atom disintegrates(falls over). This is radio activity a larger atom breaking down into smaller atoms with the release of energy and particles.

Answer 2

There is what is called a "vacuum fluctuation" (sounds like hocus-pocus, doesn't it?), which is given some responsibility for spontaneous decay. This is a quantum event - a matter of chance. Decay can also happen from other things, such as a collision with a neutron, itself probably from spontaneous decay.

Radioactive atoms are inherently unstable. The instability results from the numbers of protons and neutrons in the atom being incompatible for stability (hardly a technical term). The instability is connected with a force that acts to drive the atom apart, called the weak nuclear force. That force is counteracted by a force binding atoms together, called the strong nuclear force. In a radioactive atom, the two sit in a state of imbalance, rather like snow on a mountain side, just waiting to go into an avalanche.

The atom gets exposed to the mysterious vacuum fluctuation, or more easily understood, to such an event as a collision from a neutron. And this causes it to fly apart.

A stable atom would, of course, remain intact under similar circumstances.

Answer 3

Some atoms are radioactive because their nuclei are unstable and "break down" in time. The nucleus of an atom is composed of protons and neutrons, and it is held together by the residual strong force (or nuclear glue, if you like). Remember that protons don't like each other (opposite charges repel), and the only way a nucleus stays together to begin with is that in the fusion process some of the mass of each proton and neutron in the nucleus is converted into that binding energy. The results of fusion depend on what is fused, but some combinations of protons and neutrons, though they "survive" the fusion process and come away in one piece, just won't stay together because the particles in the nucleus, because of both their numbers and ratios, don't want to be there. Instability results, and the nucleus will break down eventually in one of several different ways (called nuclear decay schemes). As we look up and down the Periodic Table, we can see different isotopes of different elements hiding in the shadows. If we apply our knowledge and our observations, we can create what is called the Table of Nuclides to bring the different isotopes out of the shadows and give each one a "square" or "tile" on the chart and list its characteristics. Some isotopes of an element are stable, but some are not. And some unstable (radioactive) isotopes of elements exist in nature, and some don't (and have been synthesized in the physics lab). For every element, there are a number of isotopes that have been observed. The list is fairly long. Use the link below to see a table of nuclides.
Because the nucleus of some atoms are unstable.

Answer 4

There is an unbalance in the build of the atom(There are too many or too little neutrons in comparison to the protons) The half-life is the time that it takes for the proton:neutron ratio to even out. As far as i know, there are no exact reasons why normal atoms become radioactive except for making isotopes which is somehow adding or subtracting neutrons. Certain atoms (those listed radioactive on PTOE) are probably radioactive due to their natural atomic structure.

P.S. my favourite isotope is Gallium-64

P.P.S. I am only 13 years old :)

Answer 5

The radioactive isotopes are unstable and emit radiations.