A common form of elemental phosphorus is the tetrahedral P4 molecule, where all four phosphorus

A common form of elemental phosphorus is the tetrahedral P4...

A common form of elemental phosphorus is the tetrahedral $\mathrm{P}_{4}$ molecule, where all four phosphorus atoms are equivalent: At room temperature phosphorus is a solid. (a) Do you think there are any unshared pairs of electrons in the $\mathrm{P}_{4}$ molecule? (b) How many $\mathrm{P}-\mathrm{P}$ bonds are there in the molecule? (c) Can you draw a Lewis structure for a linear $\mathrm{P}_{4}$ molecule that satisfies the octet rule? (d) Using formal charges, what can you say about the stability of the linear molecule vs. that of the tetrahedral molecule?

Key Concepts

Bonding and Electron Pair Distribution

This involves understanding how atoms share electrons to form chemical bonds and how lone pairs (unshared electrons) remain localized on atoms. This analysis is critical when determining the number of bonds in a molecule and predicting the molecular geometry, which directly impacts the molecule's stability.

Formal Charge

Formal charge calculation assigns charge values to atoms based on their valence electrons, bond electrons, and lone pairs. Evaluating formal charges enables chemists to compare the relative stability of different structural isomers by favoring structures with lower absolute formal charges.

Octet Rule

The octet rule is a guideline that atoms tend to form bonds in such a way that each atom has eight electrons in its valence shell. While this rule is most strictly applied to second?period elements, it is used as a model for constructing electron configurations in molecules and assessing possible structural isomers.

Lewis Structures

Lewis structures provide a diagrammatic method to represent the bonds between atoms and the lone pairs of electrons in a molecule. Crafting a Lewis structure helps in visualizing how electrons are shared or remain unshared, and whether the molecule satisfies the octet rule.

Molecular Geometry

This concept involves the three?dimensional arrangement of atoms in a molecule. It is essential for understanding why the tetrahedral arrangement minimizes electron repulsion in molecules like P?, as dictated by the Valence Shell Electron Pair Repulsion (VSEPR) theory.

Transcript

00:01 We are given a diagram that looks much better than this, but i've tried to draw it here.

00:06 A common form of elemental phosphorus is tetrahedral p4 molecule.

00:17 And i've tried to draw a little diagram here.

00:21 Where all four phosphorus atoms are equivalent.

00:24 At room temperature, this is a solid.

00:27 Question a says, do you think there are any unshared pairs of electrons? question b asks how many p, jazz, p bonds are there? and question c says, can you draw a lewis structure? wait here.

01:03 Okay, so i'm going to first draw my lewis structure for this.

01:05 And you can see that i'm going to draw another one of these right down here.

01:10 P bond, bond, bond, p, p, p.

01:20 So if you count my bonds here, we can see that there are, as in part b, there are six p, p, p.

01:29 Bonds.

01:32 Each of these bonds is two electrons so each one of these phosphorus has an unshared pair of electrons.

01:38 So the answer for a is yes.

01:42 There are unshared electrons.

01:46 C asks us if we can draw a lewis structure for a linear and i did draw lewis structure for a linear and what i did i did my for p there are four p atoms.

02:04 4 p they each need 8 electrons for an octet is 32.

02:09 We have 4 p atoms that each have 5 for 20.

02:14 We subtract, we get 12, we divide by 2, we get 6.

02:19 There needs to be 6 bonds, linear.

02:25 If i put one bond between each, there's 3, and if i do double bonds, 4, 5, 6...

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