Markovnikov's rule

Markovnikov's rule is a principle in organic chemistry that describes the regioselectivity of the addition of protic acids (like HBr or HCl) to alkenes. It states that when a hydrogen halide adds to an asymmetrical alkene, the hydrogen atom will preferentially attach to the carbon atom that has the greater number of hydrogen atoms already attached, while the halide (e.g., Br, Cl) will attach to the carbon atom with fewer hydrogen atoms.