Why does uranium decay

The original nucleus is called the parent, while the resulting nucleus or nuclei are called the daughter or daughters. The daughters might still be radioactive , eventually breaking into more parts, or they might be stable. There are three forms of radioactive decay: which of these an atomic nucleus undergoes depends on the nature of the internal instability.

Some isotopes can decay via more than one pathway. In alpha decay, the nucleus ejects an alpha particle, which is essentially a helium nucleus two protons and two neutrons , decreasing the atomic number of the parent by two and the mass number by four.

In beta decay, a stream of electrons, called beta particles, are ejected from the parent, and a neutron in the nucleus is converted into a proton. The mass number of the new nucleus is the same, but the atomic number increases by one. In gamma decay, the atomic nucleus releases excess energy in the form of high-energy photons electromagnetic radiation. The atomic number and mass number remain the same, but the resulting nucleus assumes a more stable energy state. A radioactive isotope is one that undergoes radioactive decay.

The term "stable" is more ambiguous, as it applies to elements that don't break apart, for practical purposes, over a long span of time. This means stable isotopes include those that never break, like protium consists of one proton, so there's nothing left to lose , and radioactive isotopes, like tellurium , which has a half-life of 7. Radioisotopes with a short half-life are called unstable radioisotopes. You might assume that a nucleus in stable configuration would have the same number of protons as neutrons.

For many lighter elements, this is true. For example, carbon is commonly found with three configurations of protons and neutrons, called isotopes. The number of protons does not change, as this determines the element, but the number of neutrons does: Carbon has six protons and six neutrons and is stable; carbon also has six protons, but it has seven neutrons; carbon is also stable. However, carbon, with six protons and eight neutrons, is unstable or radioactive.

The number of neutrons for a carbon nucleus is too high for the strong attractive force to hold it together indefinitely. But, as you move to atoms that contain more protons, isotopes are increasingly stable with an excess of neutrons. This is because the nucleons protons and neutrons aren't fixed in place in the nucleus, but move around, and the protons repel each other because they all carry a positive electrical charge.

The neutrons of this larger nucleus act to insulate the protons from the effects of each other. The ratio of neutrons to protons, or N:Z ratio, is the primary factor that determines whether or not an atomic nucleus is stable.

There are also what are called magic numbers, which are numbers of nucleons either protons or neutrons that are especially stable. Each series has its own unique decay chain. The decay products within the chain are always radioactive. Only the final, stable atom in the chain is not radioactive.

Some decay products are a different chemical element. Every radionuclide has a specific decay rate, which is measured in terms of " half-life half-life The time required for half of the radioactive atoms present to decay or transform. Some radionuclides have half-lives of mere seconds, but others have half-lives of hundreds or millions of years. Some radionuclides have half-lives of mere seconds, but others have half-lives of hundreds or millions or billions of years.

Source: U. Skip to main content. Radiation Protection. Contact Us. Radioactive Decay. Two decay chains are shown below: Uranium Chemistry Nuclear Chemistry Nuclear Chemistry.

May 29, Explanation: A nucleus of uranium decays by alpha emission to form a daughter nucleus, thorium See Below. Explanation: Big stuff like Uranium usually undergoes alpha particle decay. Related questions What are radioactive isotopes?

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