Which species has the smaller bond angle, ClO₄^- or ClO₃^- ? Explain.

Verified step by step guidance

1. Identify the central atom in each species: ClO4^- and ClO3^- both have chlorine (Cl) as the central atom.
2. Determine the number of electron domains around the central atom: ClO4^- has four oxygen atoms bonded to Cl, while ClO3^- has three oxygen atoms and one lone pair on Cl.
3. Use VSEPR theory to predict the molecular geometry: ClO4^- has a tetrahedral geometry, while ClO3^- has a trigonal pyramidal geometry due to the lone pair.
4. Recall that lone pairs repel more strongly than bonding pairs, causing bond angles to decrease in the presence of lone pairs.
5. Conclude that ClO3^- has a smaller bond angle than ClO4^- because the lone pair on ClO3^- causes greater repulsion, reducing the bond angle compared to the tetrahedral angle in ClO4^- which has no lone pairs.

Key Concepts

VSEPR Theory

Valence Shell Electron Pair Repulsion (VSEPR) Theory is a model used to predict the geometry of molecules based on the repulsion between electron pairs around a central atom. According to this theory, electron pairs, whether bonding or non-bonding, will arrange themselves to minimize repulsion, which directly influences bond angles.

Resonance Structures

Resonance structures are different ways of drawing the same molecule that show the delocalization of electrons. In the case of ClO3- and ClO4-, resonance can affect the distribution of electron density and the overall geometry, which in turn influences the bond angles between the chlorine and oxygen atoms.

Hybridization

Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. The hybridization state of the central atom, chlorine in this case, determines the geometry and bond angles of the molecule. ClO4- is typically sp3 hybridized, while ClO3- can exhibit sp2 hybridization, leading to different bond angles.