If a nucleus still has excess energy after attempts of stabilization, it can emit energy without changing the number of protons or neutrons. This process is named isomeric transition. One way of isomeric transition is the emission of a gamma rays, the other competing way is internal conversion, where the excess energy of the nucleus must exceed the binding energy of an electron, which then will be ejected from the atom.

See also Decay, Gamma Radiation and Internal Conversion.

Isotones are atoms where the nuclei contain the same number of neutrons.

Isotopes of a given element have the same number of protons but a different number of neutrons in the core. Isotopes have the same electronic structure as the given element and thus have a nearly identical chemical behavior. Larger elements tend to have more stable isotopes than smaller ones.
For example, I123, I125 and I131 are isotopes of iodine; they have a different mass number.

Isotropic means that properties at any point within a medium are equal in all directions.

Isovist® is a nonionic x-ray contrast agent. Isovist® is suitable for intrathecal applications for example CT myelography, cisternography, the evaluation of cerebrospinal fluid (CSF) circulation and for use in other body cavities. Opacification is directly visible after administration of Iotrolan to the spinal subarachnoid space and various open body cavities. Isovist® flows with the CSF through the arachnoid villi into the venous blood.