Isosteres are molecules or ions with the same number of atoms and the same number of valence electrons.
Perhaps this line should be edited to fit the first example (F and H) which certainly do not have the same number of valence electrons . . . Nickthechemist 18:41, 15 October 2007 (UTC)
The 23 Nov. 2016 edit by StudentofMassey introduced a completely different concept of "isostere" to this article. I suggest that if more info can be added for both concepts, the article should be split into "Isostere_(biochemistry)" and "Isostere_(physical_chemistry)". Mr. Goodwraith 23:42, 27 April 2017 (UTC)