<P> The uncharged H 2C = C =O (ethenone) and H 2N - CN (cyanamide) molecules and the zwitterionic H 2C = N + = N − (diazomethane) molecule are isoelectronic . </P> <P> CH 3COCH 3 (acetone) and CH 2CH 3 (dimethyl diazene) are not isoelectronic . They do have the same number of nuclei and the same number of valence electrons, but the atoms' connectivity is different: the first one has both methyl (CH 3) groups attached to carbonyl's (CO's) carbon atom, forming a branched trigonal planar shape: H C-C (= O) - CH; the second molecule's structure has a consecutive attachment of the main atoms: H C-N = N - CH and its methyl groups are not connected to the same nitrogen atom . </P> <P> The amino acids tellurocysteine, selenocysteine, cysteine and serine are also considered (at least valence) isoelectronic . </P>

Is it possible for two different neutral atoms to be isoelectronic