Final answer:
In mass spectroscopy, the M+2 peak indicates isotope distribution, representing isotopes that are two mass units heavier than the primary isotope, such as carbon-13 in relation to carbon-12.
Step-by-step explanation:
In mass spectroscopy, the M+2 peak typically indicates c) Isotope distribution. This peak is observed due to the presence of isotopes that are heavier by two mass units than the most abundant isotope contributing to the molecular ion (M+) peak. For example, in a sample containing carbon, the M+ peak represents the molecule containing the most common isotope of carbon, carbon-12, while the M+2 peak would represent molecules that include one or more atoms of carbon-13, which is heavier by one neutron.
Mass spectrometry is a powerful analytical technique used to determine the mass-to-charge ratio of ions. The presence of M+2 peaks in the mass spectrum is an essential aspect of MS analysis, as it provides information about the isotopic composition of a molecule, which is critical for accurate molecular identification and quantitation in various applications such as chemistry, forensics, and environmental science.