What makes a chemical radioactive?

Answer 1

An element is radioactive if its atomic nuclei are unstable. The nucleus contains protons and neutrons; the electromagnetic force pushes the protons apart because they have the same charge, but the strong nuclear force pulls the protons and neutrons together. A nucleus is only stable if it has the right balance of protons and neutrons, and doesn't have any extra energy (if it does, it is said to be in an excited state).

An unstable nucleus will sooner or later change its state by undergoing radioactive decay. There are many kinds of radioactive decay, but four are particularly well known:

* The nucleus may eject a cluster of two protons and two neutrons, which is called an alpha particle.

* A neutron may convert into a proton by emitting an electron (in this context called a beta particle) and an antineutrino.

* An excited nucleus may release energy in the form of a photon, called a gamma ray.

* The nucleus may break up into two or more smaller nuclei, typically releasing one or more neutrons in the process; this is called spontaneous fission.

Answer 2

Radioactivity is caused by atoms whose nuclei are unstable. Such unstable atoms may change into other atoms through a process called radioactive decay. This process produces radiation such as gamma rays, or alpha and beta radiation. (all of which are harmful to humans)

There are multiple ways in which an unstable nuclei can change. In one example a neutron in the nucleus may convert to a proton, an electron and an anti-electron neutrino. This causes the atom number to increase (since this is the number of protons in the nucleus). The emitted electron is perceived as beta (minus) radiation.

Some elements, such as uranium are intrinsically radioactive. They were never 'made' radioactive. Other elements, such as lead, can be made radioactive by bombarding them with energetic radiation (such as another radioactive source). In this process the lead is changed to another isotope of lead, or another (possibly radioactive) element.

An example of this happens in the storage of radioactive materials. Such materials are usually sealed in lead containers (lead is very dense so it blocks the radiation from getting out the container). But after many years the lead needs to be replaced because it has gotten radioactive itself by constant exposure to the stuff inside the lead container.

Answer 3

In general, the heavier an atom is, the more likely it is to be radioactive, since the strong nuclear force that hold a nucleus together is extremely short range, and begins to break down when the nucleus is too large. At a certain nuclear size, the electrical repulsion of protons for other protons will overcome the nuclear attraction. But in addition, radioactivity can occur at smaller sizes, even as small as tritium which is just four nucleons, one proton and three neutrons. That is because for optimum effectiveness, the strong nuclear force also requires a balance between protons and neutrons. If you have three times as many neutrons as protons, that is not a stable arrangement.

Answer 4

Some isotopes are stable while others are not because of the extra neutrons in their nuclei. The ones that are unstable are radioactive. They are called radioisotopes. An example of the is Uranium-235.

Answer 5

a bunch of elements join together and make a radioactive substance

Answer 6

things which are not naturally radioactive can be made radioactive by passing alpha particles through them.

Answer 7

the emission of radiations make atom radioactive.

Answer 8

An isotope is radioactive and unstable when the ratio neutrons/protons is too big.

Answer 9

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