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Ch.8 - Basic Concepts of Chemical Bonding
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.8 - Basic Concepts of Chemical BondingProblem 105b
Chapter 8, Problem 105b

A common form of elemental phosphorus is the tetrahedral P4 molecule, where all four phosphorus atoms are equivalent: 
(b) How many P-P bonds are there in the molecule?

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1
Understand the structure of the P_4 molecule: The P_4 molecule is a tetrahedral structure, meaning it forms a shape similar to a pyramid with a triangular base.
Visualize the tetrahedral shape: In a tetrahedral P_4 molecule, each phosphorus atom is located at a vertex of the tetrahedron.
Identify the bonds: In a tetrahedral structure, each vertex (phosphorus atom) is connected to three other vertices (phosphorus atoms) by P-P bonds.
Count the bonds: Since each phosphorus atom forms bonds with three other phosphorus atoms, you might initially think there are 4 x 3 = 12 bonds.
Avoid double-counting: Each bond is shared between two phosphorus atoms, so the actual number of unique P-P bonds is 12/2 = 6.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Molecular Structure

The molecular structure of a compound refers to the arrangement of atoms within the molecule. In the case of P4, the tetrahedral geometry indicates that the four phosphorus atoms are arranged at the corners of a tetrahedron, which influences the bonding and overall stability of the molecule.
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Covalent Bonds

Covalent bonds are formed when two atoms share electrons, allowing them to achieve a more stable electron configuration. In P4, each phosphorus atom forms single covalent bonds with the other three phosphorus atoms, resulting in a network of interconnected atoms.
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Counting Bonds

To determine the number of bonds in a molecule, one must consider how many pairs of atoms are connected. In P4, each of the four phosphorus atoms is bonded to three others, leading to a total of six P-P bonds, as each bond is counted once for each pair of atoms.
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Related Practice
Textbook Question

A common form of elemental phosphorus is the tetrahedral P4 molecule, where all four phosphorus atoms are equivalent: 

Draw a Lewis structure for a linear P4 molecule that satisfies the octet rule. Does this molecule have resonance structures?

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Textbook Question

Ortho-Dichlorobenzene, C6H4Cl2, is obtained when two of the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. (b) Are there any resonance structures for the molecule? If so, sketch them.

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Textbook Question

Ortho-Dichlorobenzene, C6H4Cl2, is obtained when two of the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. (a) Complete a Lewis structure for the molecule using bonds and electron pairs as needed.

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Textbook Question

Two compounds are isomers if they have the same chemical formula but different arrangements of atoms. Use Table 8.3 to estimate H for each of the following gas-phase isomerization reactions and indicate which isomer has the lower enthalpy. (d) Methyl isocyanide → Acetonitrile

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