Helium :For other uses of this term, see Helium (disambiguation) .
Helium (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas series in the periodic table and whose atomic number is 2. Its boiling and melting points are the lowest more
The aldol reaction is an important carbon-carbon bond formation reaction in organic chemistry .
In its usual form, it involves the nucleophilic addition of a ketone enolate to an aldehyde to form a β-hydroxy ketone, or "aldol" (aldehyde + alcohol), a structural unit foun more
Trade and use of saffron
(大阪府), Kansai , Honshū , Japan .
Saffron has been used as a seasoning , fragrance , dye , and medicine for more than 3,000 years.. The world's most expensive spice by weight, saffron consists of stigmas plucked from the saffron crocus (Crocus sativus). The resulting more
Ammolite is a rare and valuable opal -like organic gemstone found primarily along the eastern slopes of the Rocky Mountains of the United States and Canada . It is made of the fossil ized shells of ammonite s, which in turn are composed primarily of aragonite , the same mineral that m more
Hydrogen (), is the chemical element represented by the symbol H and an atomic number of 1. At standard temperature and pressure it is a colourless, odorless, nonmetal lic, tasteless, highly flammable diatomic gas (H2).
With an atomic mass of 1.00794 amu, hydrogen is th more