Question

Write a Lewis structure for (a) \(\mathrm{XeF}_{3}{ }^{+}\) (b) \(\mathrm{PCl}_{4}^{+}\) (c) \(\mathrm{BrF}_{5}\) (d) \(\mathrm{HPO}_{4}^{2-}(\) no \(\mathrm{P}-\mathrm{H}\) or \(\mathrm{O}-\mathrm{O}\) bonds \()\)

Short answer

Question: Draw the Lewis structures for the following species: (a) XeF₃⁺ (b) PCl₄⁺ (c) BrF₅ (d) HPO₄²⁻ (no P-H or O-O bonds). Answer: (a) XeF₃⁺: The Lewis structure for XeF₃⁺ has xenon (Xe) as the central atom surrounded by three fluorine (F) atoms, and two lone pairs on Xe. No formal charges are required. (b) PCl₄⁺: The Lewis structure for PCl₄⁺ has phosphorus (P) as the central atom connected to four chlorine (Cl) atoms. Each Cl atom has three lone pairs. No formal charges are required. (c) BrF₅: The Lewis structure for BrF₅ has bromine (Br) as the central atom connected to five fluorine (F) atoms. Each F atom has three lone pairs and Br has one lone pair. No formal charges are required. (d) HPO₄²⁻: The Lewis structure for HPO₄²⁻ has phosphorus (P) as the central atom connected to four oxygen (O) atoms. Three of the O atoms have three lone pairs and -1 formal charge, while the remaining O is connected to a hydrogen (H) atom with two lone pairs and no charge. The overall charge of HPO₄²⁻ is 2-.

Step-by-step solution

Determine the central atom.

Xe is the central atom.

Calculate the total number of valence electrons.

Xe: 8 valence electrons + 1 for the positive charge, F: 7 valence electrons (each). Total = 8 + 1 + 3*7 = 30 valence electrons.

Draw single bonds between central and surrounding atoms.

Xe is connected to three F atoms: Xe-F bonds.

Distribute remaining electrons.

Each Xe-F bond uses 2 electrons, so we have used 6 electrons. We have 24 left to distribute as lone pairs around F atoms (2 lone pairs for each F).

Make sure each atom has an octet structure.

Xe has only 6 electrons (does not follow octet rule), so we add 2 lone pairs on Xe.

Check for formal charges.

No formal charges needed, as XeF\(_{3}^{+}\) already has a positive charge. (b) For PCl\(_{4}^{+}\):

Determine the central atom.

P is the central atom.

Calculate the total number of valence electrons.

P: 5 valence electrons + 1 for the positive charge, Cl: 7 valence electrons (each). Total = 5 + 1 + 4*7 = 34 valence electrons.

Draw single bonds between central and surrounding atoms.

P is connected to four Cl atoms: P-Cl bonds.

Distribute remaining electrons.

Each P-Cl bond uses 2 electrons, so we have used 8 electrons. We have 26 left to distribute as lone pairs around Cl atoms (3 lone pairs for each Cl).

Make sure each atom has an octet structure.

P has only 8 electrons.

Check for formal charges.

No formal charges needed, as PCl\(_{4}^{+}\) already has a positive charge. (c) For BrF\(_{5}\):

Determine the central atom.

Br is the central atom.

Calculate the total number of valence electrons.

Br: 7 valence electrons, F: 7 valence electrons (each). Total = 7 + 5*7 = 42 valence electrons.

Draw single bonds between central and surrounding atoms.

Br is connected to five F atoms: Br-F bonds.

Distribute remaining electrons.

Each Br-F bond uses 2 electrons, so we have used 10 electrons. We have 32 left to distribute as lone pairs around F atoms (3 lone pairs for each F) and Br (1 lone pair).

Make sure each atom has an octet structure.

All atoms follow the octet rule in this case.

Check for formal charges.

No formal charges needed. (d) For HPO\(_{4}^{2-}\):

Determine the central atom.

P is the central atom.

Calculate the total number of valence electrons.

P: 5 valence electrons, O: 6 valence electrons (each), H: 1 valence electron + 2 for the negative charge. Total = 5 + 4*6 + 1 + 2 = 32 valence electrons.

Draw single bonds between central and surrounding atoms.

P is connected to four O atoms: P-O bonds. One of the O atoms is also connected to H: O-H bond.

Distribute remaining electrons.

Each P-O bond uses 2 electrons and the O-H bond uses 2 electrons, so we have used 10 electrons. We have 22 left to distribute as lone pairs: 1 lone pair on P, 2 lone pairs on the H-connected O atom, and 3 lone pairs on the other three O atoms.

Make sure each atom has an octet structure.

All atoms follow the octet rule (except hydrogen).

Check for formal charges.

Two of the oxygens have a -1 formal charge, which matches with the overall 2- charge of HPO\(_{4}^{2-}\).