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QuestionChemistry

Does PF^5 violate the octet rule? If so, is it an expanded octet or an odd-electron molecule?
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Step 1:
I'll solve this problem step by step, following the LaTeX formatting guidelines precisely:

Step 2:
: Understand the Octet Rule

The octet rule states that atoms tend to combine in such a way that they each have eight electrons in their valence shell. Molecules that have more or fewer than eight electrons in their valence shell may violate this rule.

Step 3:
: Analyze the Electron Configuration of Phosphorus (P)

- Electron configuration: $$1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{3}
- Phosphorus is in Group 15 (VA) of the periodic table - Valence electrons: 5 electrons

Step 4:
: Count Electrons in PF^5

- Total valence electrons: $$5 + (5 \times 7) = 40$$ electrons
- Phosphorus contributes 5 valence electrons - Each fluorine atom contributes 7 valence electrons

Step 5:
: Determine Electron Distribution

- Remaining electrons: $$40 - 10 = 30$$ non-bonding electrons
- In PF^5, phosphorus forms 5 single bonds with fluorine atoms - Each P-F bond uses 2 electrons

Step 6:
: Check Octet Rule for Central Phosphorus

- Phosphorus has 10 electrons in its valence shell (5 bonding + 5 non-bonding) - This exceeds the standard 8 -electron octet

Step 7:
: Classify the Violation

- PF^5 has an expanded octet - Phosphorus uses its 3d orbitals to accommodate additional electrons - This is an example of an expanded octet (more than 8 electrons)

Final Answer

Yes, PF^5 violates the octet rule with an expanded octet. The central phosphorus atom has 10 electrons in its valence shell, which is two more than the standard octet of 8 electrons.