In the cyanate ion, OCN^-, carbon is the central atom. (a)...

In the cyanate ion, OCN$^{-}$, carbon is the central atom. (a) Draw as many resonance structures as you can for OCN$^{-}$, and assign formal charges to the atoms in each. (b) Which resonance structure makes the greatest contribution to the resonance hybrid? Which makes the least contribution? Explain. (c) Is OCN$^{-}$ linear or bent? Explain. (d) Which hybrid orbitals are used by the C atom, and how many $\pi$ bonds does the C atom form?

In the cyanate ion, OCN$^{-}$, carbon is the central atom.
(a) Draw as many resonance structures as you can for OCN$^{-}$, and assign formal charges to the atoms in each.
(b) Which resonance structure makes the greatest contribution to the resonance hybrid? Which makes the least contribution? Explain.
(c) Is OCN$^{-}$ linear or bent? Explain.
(d) Which hybrid orbitals are used by the C atom, and how many $\pi$ bonds does the C atom form?

Key Concepts

Molecular Geometry (VSEPR Theory)

Molecular geometry refers to the three-dimensional arrangement of atoms in a molecule, commonly predicted using VSEPR (Valence Shell Electron Pair Repulsion) theory. This theory explains that electron pairs repel each other, resulting in specific molecular shapes such as linear or bent configurations, depending on the number and arrangement of bonding and lone pairs around the central atom.

Resonance Hybrid Contributions

The contribution of each resonance structure to the overall resonance hybrid is determined by its relative stability. Structures with minimized formal charges, complete octets, and negative charges on highly electronegative atoms tend to contribute more significantly, while those with high charge separation or unfavorable charge distribution contribute less.

Hybridization and Orbital Overlap

Hybridization is a model that describes the mixing of atomic orbitals to form new hybrid orbitals that are used in the bonding process. This concept helps explain the geometry of molecules by accounting for the directional nature of bonds, such as sigma bonds formed from hybrid orbitals and pi bonds formed from the overlap of unhybridized p orbitals. Understanding hybridization is key to predicting how many bonds (both sigma and pi) a central atom can form.

Resonance Structures

Resonance structures are alternate Lewis structures for a molecule that differ only in the distribution of electrons, not in the placement of the atoms. They demonstrate that the true electronic structure is a hybrid of multiple forms, with electron delocalization that can explain bonding patterns that cannot be represented by a single Lewis structure.

Formal Charge Calculation

Formal charge calculation is a method used to estimate the electron distribution within a molecule by assigning electrons between atoms based on a set of rules. This calculation is essential for evaluating the stability of different resonance structures, with lower formal charges and placement of negative charges on more electronegative atoms often indicating greater stability.

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