Titanium belongs to the group of elements known as transition metals, known for their variable valence and oxidation states. That is, the electrons in these elements can inhabit various orbits around the nucleus, and the elements gain or lose varying numbers of electrons when bonding with other elements.
Titanium is number 22 on the periodic table and contains 22 protons in the nucleus. Its atomic weight is 47.88, an average taken from a range of 46 to 50 atomic units of mass.
Titanium does not typically react to gas at normal atmospheric temperatures but becomes highly reactive at higher temperatures. It combusts when exposed to air at 2200 degrees Fahrenheit (1204 degrees Celsius), which is under its melting point of 3034 F (1668 C). In pure oxygen, the ignition point is 1130 F (610 C). Titanium bonds with oxygen at temperatures exceeding 950 degrees Fahrenheit (510 C), creating a number of oxides ranging from TiO to Ti7O12. Similarly, nitrogen bonds with titanium at higher temperatures, though both tend toward surface-only reactions that create an oxide, or nitride scale, on the outer layers. Deeper penetration occurs when the temperature exceeds 1300 F (704 C).
Titanium is also reactive with hydrochloric and sulfuric acids, though the reaction is slow unless heat is applied.