Talk:PH

Proton

http://en.wikipedia.org/wiki/Proton#Hydrogen_ion

In chemistry, the term proton refers to the hydrogen ion, H+. Since the atomic number of hydrogen is 1, a hydrogen ion has no electrons and corresponds to a bare nucleus, consisting of a proton (and 0 neutrons for the most abundant isotope protium 1 1H). The proton is a "bare charge" with only about 1/64,000th of the radius of a hydrogen atom, and so is extremely reactive chemically. The free proton thus has an extremely short lifetime in chemical systems such as liquids and it reacts immediately with the electron cloud of any available molecule.

en.wikipedia.org/wiki/Proton

The proton is a subatomic particle with the symbol p or p+ and a positive electric charge of 1 elementary charge.

Free protons exist in plasmas in which temperatures are too high to allow them to combine with electrons. Free protons of high energy and velocity make up 90% of cosmic rays, which propagate in vacuum for interstellar distances.

http://en.wikipedia.org/wiki/Star_formation#Interstellar_clouds

A spiral galaxy like the Milky Way contains stars, stellar remnants and a diffuse interstellar medium (ISM) of gas and dust. The latter consists of about 0.1 to 1 particles per cm3 and is typically composed of roughly 70% hydrogen by mass, with most of the remaining gas consisting of helium.

In the dense nebulae where stars are produced, much of the hydrogen is in the molecular (H2) form, so these nebulae are called molecular clouds.