;1857 : Friedrich August Kekul?von Stradonitz proposes that carbon is tetravalent, or forms exactly four chemical bonds.
22.
He proposed that carbon atoms were tetravalent, and could bond to themselves to form the carbon skeletons of organic molecules.
23.
It is an onium ion because of its tetravalent nitrogen atom and + 1 charge, similar in that regard to ammonium.
24.
Carbon atoms are tetravalent, forming four covalent bonds with other atoms, whereas hydrogen atoms bond with only one other atom.
25.
First used in 1945, the tetravalent vaccine was not widely distributed, since its deployment coincided with the discovery of penicillin.
26.
Gomberg postulated that some non-tetravalent carbon structure existed in solution because of the observed activity towards oxygen and the halogens.
27.
Owing to thorium ( IV )'s lack of electrons in 6d and 5f orbitals, the tetravalent thorium compounds are colourless.
28.
The tetravalent americium ( IV ) fluoride ( AmF 4 ) is obtained by reacting solid americium ( III ) fluoride with molecular fluorine:
29.
The most stable coordination compounds of actinides tetravalent thorium and uranium are obtained in reactions with diketones, e . g . acetylacetone.
30.
TDEN PIV is inactivated tetravalent vaccine undergoing phase I trials as part of a collaboration between GSK and the Walter Reed Army Institute of Research.
