The first financial model to use a Markov chain was from Prasad et al. in 1974. Another was the regime-switching model of James D. Hamilton (1989), in which a Markov chain is used to model switches between periods of high volatility and low volatility of asset returns.
A molecule is a particle containing two or more atoms. If it contains only one type of atom it is called an element.
A molecule is two or more ATOMS (composed of protons (+) and neutrons (0) to make the nucleus, and orbited by electrons (-) bonded together. They may be the same type of atom (which means that the molecule is an ELEMENT), or they may be different types of atoms (which means that the molecule is a COMPOUND).