Ch 13Nuclear Chemistry and Radioactivity — Class 11 Chemistry, concept-first.

Nuclear chemistry studies reactions and changes that take place in atomic nuclei, as opposed to ordinary chemistry, which concerns the electrons around them.

A nuclide is a specific nucleus, characterised by its exact numbers of protons and neutrons, considered on its own without reference to the surrounding electron cloud.

Beyond classifying nuclides by how their proton/neutron counts relate to each other, they can also be split into two broad groups purely on the basis of stability.

Whether the proton count and neutron count of a nuclide are each individually even or odd turns out to be a strong predictor of nuclear stability.

A second major factor governing nuclear stability is the neutron-to-proton ratio, . Plotting the neutron number against the proton number for every known stable nuclide does not give a scattered cloud…

A further, more specific pattern in nuclear stability is captured by magic numbers. Nuclides whose proton count or whose neutron count equals one of the values 2, 8, 20, 28, 50, 82 or 126 are found to…

A nucleus packs several protons together within a volume only about m across. Since all protons carry the same positive charge, the electrostatic (coulombic) repulsion between any two protons at that…

Binding energy measures how strongly the nucleons of a nucleus are held together: formally, it is the energy that would be required to break a nucleus apart into its separate, individual protons and n…

An element is radioactive if the nuclei of its atoms are unstable. Radioactivity is the phenomenon in which such an unstable nucleus spontaneously emits a nuclear particle and/or gamma radiation and,…

The rate of decay of a radioelement -- also called its activity -- is defined as the number of nuclei of its atoms that decay per unit time.

The rate law for radioactive decay states that the instantaneous rate of decay of a radioelement, at any given moment, is directly proportional to the number of undecayed nuclei present in the sample…

Starting from the rate law (section 13.5.2), rearranging gives . Integrating both sides, , gives , where is a constant of integration that is pinned down using the starting condition of the sample.

The half-life of a radioelement, , is defined as the time needed for a given number of its nuclei to decay to exactly half of their initial value.

The exponential decay law can be turned into a straight-line graph, which is often more practical to work with than the raw exponential curve.

Since the rate of radioactive decay is expressed in disintegrations per second (dps), two named units are commonly used to state it in practice.

Alpha () decay is the spontaneous emission of an alpha particle from an unstable nucleus. An alpha particle carries a charge of and a mass of -- it is, in fact, identical to a bare helium nucleus, whi…

Beta () decay is the spontaneous emission of a negatively charged, high-speed electron -- the beta particle -- from the nucleus.

Gamma () radiation is high-energy electromagnetic radiation, and it is almost always emitted TOGETHER WITH an alpha or a beta decay, rather than occurring entirely on its own.

Section 13.7 turns from natural (spontaneous) nuclear changes -- alpha decay, beta decay -- to non-spontaneous, human-induced nuclear reactions, generally called nuclear transmutations.

Induced (or artificial) radioactivity is a specific type of nuclear transmutation in which a nucleus that starts out STABLE is converted, by bombardment with a suitable particle, into a nucleus that i…

Nuclear fission is the splitting of a heavy nucleus into two nearly equal, lighter fragments, accompanied by the release of a large amount of energy.

Nuclear fusion is the combination of two lighter nuclei into a single, heavier nucleus, accompanied by the release of an enormous amount of energy -- it is fusion, not fission, that powers the Sun and…

Radiocarbon dating is a technique used to find the age of historic and archaeological ORGANIC samples -- things like old wood samples, or animal and human fossils -- by exploiting the known, steady de…

Nuclear fission offers a genuine alternative energy source to burning fossil fuels. Traditionally, the steam that drives a power-plant turbine comes from boilers fuelled by oil, gas or coal -- all of…

Hospitals and larger medical clinics typically maintain a dedicated Department of Nuclear Medicine, reflecting how central radioisotopes have become to modern healthcare -- several are routinely used…

Beyond nuclear power (section 13.8.2), radiocarbon dating (section 13.8.1) and medicine (section 13.8.3), radioisotopes find a variety of further applications across other fields.