Isomers are molecules with the same chemical formula and often with the same kinds of bonds between atoms, but in which the atoms are arranged differently.

See also Isotope.

An element consists of atoms having the same structure and the same chemically reaction.
See also Magnetic Resonance Spectroscopy, Isomer, Isotope, Helium, and Gadolinium.
Mathematically, an element or member of a set is any one of the separate objects that make up that set. Elements in arrays (parallel arrangement of many identical items) are used in MRI coils.

See also Array Coil, Array Processor, and Array Spatial Sensitivity Encoding Technique.

Atomic nuclei that contain the same number of protons, but differ in the number of neutrons in the nucleus of the atom for the element concerned. For example, 1H, 2H, and 3H are the three isotopes of hydrogen, otherwise known as proton, deuterium, and tritium. Various isotopes have different nuclear magnetic moments and different resonant frequencies. Many isotopes have no magnetic moment and are therefore not observable by MR.

See also Isomer.