Which contribution to the body of scientific knowledge is most recent? the development of the lever
the discovery of the structure of DNA
the discovery
of electricity
the theory of evolution

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.

i just learnt this recently but i need to look through my notes again