A Dalton (Da) is a unit of mass used in the field of chemistry and molecular biology to express the molecular weight or mass of atoms, molecules, and compounds. It is named after John Dalton, a British chemist and physicist who contributed to the development of modern atomic theory.
One Dalton (Da) is defined as one twelfth of the mass of an unbound carbon-12 atom, which is roughly equivalent to 1.66053906660 x 10^-27 kilograms. This definition was adopted as the standard for atomic mass units (u) and is now used internationally.
Daltons are useful in the following contexts:
Atomic and Molecular Mass: The molecular weight or mass of a molecule is often expressed in Daltons. For example, the molecular weight of water (H2O) is approximately 18.01528 Da, which means that one molecule of water has a mass of approximately 18.01528 Daltons.
Proteomics and Biochemistry: In biology, particularly in the study of proteins, the mass of biomolecules like proteins and nucleic acids is often measured in Daltons. This is important for understanding their structure and function.
Mass Spectrometry: Mass spectrometry is a powerful analytical technique used to determine the mass and composition of molecules. Mass spectrometry results are often reported in Daltons.
Chemical Reactions: In chemical reactions, the mass of reactants and products can be expressed in Daltons to understand the stoichiometry of the reaction.
The exagram (Eg) is a unit of mass in the metric system. It is equal to one quintillion (10^18) grams. The exagram is an extremely large unit of mass and is primarily used in scientific contexts when dealing with colossal quantities of matter, such as in astrophysics or geology.
To give you an idea of the scale involved, one exagram is equivalent to 1,000,000,000,000,000,000 grams or 1,000,000,000 metric tons. This unit is rarely encountered in everyday life but is valuable when measuring the mass of massive celestial bodies, geological formations, or other incredibly large objects in the universe.