Find the total number of pairs of isoelectronic species $(ONF, ONO^{-}); (CO_{2}, NO_{2}^{\oplus}), (Mg^{+ 2}, N^{- 3}), (N_{2} O, NO_{2}^{\oplus}), (CH_{4}, NH_{4}^{\oplus}),$
$(Mn^{+ 2}, Fe^{+ 3})$

Question

Find the total number of pairs of isoelectronic species $(ONF, ONO^{-}); (CO_{2}, NO_{2}^{\oplus}), (Mg^{+ 2}, N^{- 3}), (N_{2} O, NO_{2}^{\oplus}), (CH_{4}, NH_{4}^{\oplus}),$

$(Mn^{+ 2}, Fe^{+ 3})$

TestHub · Accepted Answer

Isoelectronic species have the same total number of electrons. Count the electrons in each species.

(ONF, ONO⁻): ONF = 8 + 7 + 9 = 24; ONO⁻ = 8 + 7 + 8 + 1 = 24. Isoelectronic.

(CO₂, NO₂⁺): CO₂ = 6 + 2×8 = 22; NO₂⁺ = 7 + 2×8 − 1 = 22. Isoelectronic.

(Mg²⁺, N³⁻): Mg²⁺ = 12 − 2 = 10; N³⁻ = 7 + 3 = 10. Isoelectronic.

(N₂O, NO₂⁺): N₂O = 2×7 + 8 = 22; NO₂⁺ = 7 + 2×8 − 1 = 22. Isoelectronic.

(CH₄, NH₄⁺): CH₄ = 6 + 4×1 = 10; NH₄⁺ = 7 + 4×1 − 1 = 10. Isoelectronic.

(Mn²⁺, Fe³⁺): Mn²⁺ = 25 − 2 = 23; Fe³⁺ = 26 − 3 = 23. Isoelectronic.

All 6 pairs are isoelectronic. Answer: 6

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