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An ionic compound of sodium cations and hydrogen anions. Its oxidation state assignments are $+1$ for sodium and $-1$ for hydrogen.

Transfer of a solute between immiscible liquid phases according to its relative chemical affinities. complexation and oxidation state can change the distribution; selective back-extraction is often called stripping. Extraction efficiency alone does not establish separation from a second solute.

The spectrochemical series orders ligands empirically by the splitting they produce in comparable complexes. Pi-donor ligands tend toward smaller splittings and pi-acceptor ligands toward larger ones. Metal, geometry and oxidation state still matter; a sigma-basicity scale is not an interchangeable substitute.

A sulfide ion is formally ${\mathrm{S}}^{2-}$. Relative to oxide it is larger, more polarizable and more readily oxidized; the ability of a metal to support a high oxidation state need not survive replacement of oxygen by sulfur.

The +2 oxidation state of tin. The actual aqueous species can depend on pH, hydrolysis and ligands; a bare ionic formula is an analytical shorthand.

The +4 oxidation state of tin. The actual aqueous species can depend on pH, hydrolysis and ligands; a bare ionic formula is an analytical shorthand.

A transition metal has an incompletely filled d subshell in its atom or a relevant cation. Its metal–ligand orbital interactions support varied oxidation states, magnetic states and coordination geometries.

A neutral oxygen-donor extractant, $\mathrm{OP}(\mathrm{OBu}{)}_3$, often abbreviated TBP. It can solvate metal nitrate species in solvent extraction. Selectivity depends on acidity, metal oxidation state, diluent and subsequent stripping conditions.