isostere

noun

iso·​stere ˈī-sə-ˌsti(ə)r 

variants also isoster

ˈī-sə-ˌster 

: one of two or more substances (as carbon monoxide and molecular nitrogen) that exhibit similarity of some properties as a result of having the same number of total or valence electrons in the same arrangement and that consist of different atoms and not necessarily the same number of atoms

isosteric

ˌī-sə-ˈsti(ə)r-ik  -ˈster- 

adjective

isosterism

ī-ˈsäs-tə-ˌriz-əm 

noun