section_path: Properties/Compounds/Protons and acids
section_name: Protons and acids
paragraph_text: Protons and acids
  
  Oxidation of hydrogen removes its electron and gives H, which contains no electrons and a nucleus which is usually composed of one proton. That is why H is often called a proton. This species is central to discussion of acids. Under the Brønsted–Lowry acid–base theory, acids are proton donors, while bases are proton acceptors.
  
  A bare proton, H, cannot exist in solution or in ionic crystals because of its strong attraction to other atoms or molecules with electrons. Except at the high temperatures associated with plasmas, such protons cannot be removed from the electron clouds of atoms and molecules, and will remain attached to them. However, the term 'proton' is sometimes used loosely and metaphorically to refer to positively charged or cationic hydrogen attached to other species in this fashion, and as such is denoted " H " without any implication that any single protons exist freely as a species.
  
  To avoid the implication of the naked "solvated proton" in solution, acidic aqueous solutions are sometimes considered to contain a less unlikely fictitious species, termed the " hydronium ion" (). However, even in this case, such solvated hydrogen cations are more realistically conceived as being organized into clusters that form species closer to. Other oxonium ions are found when water is in acidic solution with other solvents.
  
  Although exotic on Earth, one of the most common ions in the universe is the H + 3 ion, known as protonated molecular hydrogen or the trihydrogen cation.