Consider the following statements about the rules for naming coordination compounds.
(A) The cation is named first in both positively and negatively charged coordination entities.
(B) The ligands are named in an alphabetical order after the name of the central atom/ion.
(C) Names of the anionic ligands end in –o, while the neutral ligands CO and NO are named carbonyl and nitrosyl.
(D) The oxidation state of the metal in a cation, anion or neutral coordination entity is indicated by an Arabic numeral in parenthesis.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A) and (C) only
Coordination compounds are named by additive nomenclature: the ligands are listed as prefixes to the name of the central atom, and the oxidation state of the metal follows in brackets.
(A) The cation is named first in both positively and negatively charged coordination entities. — True. As in any salt, the cation comes first: K3[Fe(CN)6] is potassium hexacyanidoferrate(III).
(B) The ligands are named in an alphabetical order after the name of the central atom/ion. — False. The ligands are named before the central atom: [Co(NH3)5Cl]Cl2 is pentaamminechloridocobalt(III) chloride. This order is the reverse of that used in writing the formula.
(C) Names of the anionic ligands end in –o, while the neutral ligands CO and NO are named carbonyl and nitrosyl. — True. Anionic ligands take an –o ending (chlorido, cyanido); neutral ligands keep their names except aqua, ammine, carbonyl and nitrosyl.
(D) The oxidation state of the metal in a cation, anion or neutral coordination entity is indicated by an Arabic numeral in parenthesis. — False. It is shown by a Roman numeral, as in cobalt(III), not cobalt(3).
NCERT (2026-27 edition):
5.3.2 Naming of Mononuclear Coordination Compounds – “(i) The cation is named first in both positively and negatively charged coordination entities.”
“(ii) The ligands are named in an alphabetical order before the name of the central atom/ion. (This procedure is reversed from writing formula).”
“(iii) Names of the anionic ligands end in –o, those of neutral and cationic ligands are the same except aqua for H2O, ammine for NH3, carbonyl for CO and nitrosyl for NO.”
“(v) Oxidation state of the metal in cation, anion or neutral coordination entity is indicated by Roman numeral in parenthesis.”