QQuestionChemistry
QuestionChemistry
"Write Lewis structures that obey the octet rule for each of the following. Except for HCN and H₂CO, the first atom listed is the central atom. For HCN and H₂CO, carbon is the central atom.
(a) HCN
(b) PH₃
(c) CHCl₃
(d) NH₄⁺
(e) H₂CO
(f) SeF₂
(g) CO₂
(h) O₂
(i) HBr"
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Answer
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Step 1:I'll solve this step by step, focusing on drawing Lewis structures that obey the octet rule for each molecule/ion.
(a) HCN (Hydrogen Cyanide)
Step 2:: Identify the central atom
- Carbon is the central atom
Step 3:: Count total valence electrons
- Total: $$1 + 4 + 5 = 10$$ valence electrons
- H: 1 electron - C: 4 electrons - N: 5 electrons
Step 4:: Draw Lewis structure
H - C \equiv N:
- Single bond between H and C - Triple bond between C and N - Nitrogen has a lone pair (b) PH₃ (Phosphine)
Step 5:: Identify the central atom
- Phosphorus (P) is the central atom
Step 6:: Count total valence electrons
- Total: $$5 + (3 \times 1) = 8$$ valence electrons
- P: 5 electrons - H: 3 × 1 electron
Step 7:: Draw Lewis structure
H - P:
- Three single bonds from P to H - One lone pair on P (c) CHCl₃ (Chloroform)
Step 8:: Identify the central atom
- Carbon (C) is the central atom
Step 9:: Count total valence electrons
- Total: $$4 + (3 \times 7) = 25$$ valence electrons
- C: 4 electrons - Cl: 3 × 7 electrons
Step 10:: Draw Lewis structure
H - C(Cl)_{3}:
- Single bonds from C to three Cl atoms - Single bond from C to H - Chlorine atoms have three lone pairs each (d) NH₄⁺ (Ammonium ion)
Step 11:: Identify the central atom
- Nitrogen (N) is the central atom
Step 12:: Count total valence electrons
- Total: $$5 + (4 \times 1) - 1 = 8$$ valence electrons
- N: 5 electrons - H: 4 × 1 electron - Charge: + 1 (removes one electron)
Step 13:: Draw Lewis structure
H H
| | - Four single bonds from N to H atoms (e) H₂CO (Formaldehyde)
Step 14:: Identify the central atom
- Carbon (C) is the central atom
Step 15:: Count total valence electrons
- Total: $$4 + 6 + (2 \times 1) = 12$$ valence electrons
- C: 4 electrons - O: 6 electrons - H: 2 × 1 electron
Step 16:: Draw Lewis structure
H - C = O:
- Double bond between C and O - Two single bonds from C to H atoms (f) SeF₂ (Selenium difluoride)
Step 17:: Identify the central atom
- Selenium (Se) is the central atom
Step 18:: Count total valence electrons
- Total: $$6 + (2 \times 7) = 20$$ valence electrons
- Se: 6 electrons - F: 2 × 7 electrons
Step 19:: Draw Lewis structure
F - Se - F:
- Two single bonds from Se to F atoms - Two lone pairs on Se (g) CO₂ (Carbon dioxide)
Step 20:: Identify the central atom
- Carbon (C) is the central atom
Step 21:: Count total valence electrons
- Total: $$4 + (2 \times 6) = 16$$ valence electrons
- C: 4 electrons - O: 2 × 6 electrons
Step 22:: Draw Lewis structure
O = C = O
- Two double bonds between C and O atoms (h) O₂ (Oxygen molecule)
Step 23:: Count total valence electrons
- Total: $$2 \times 6 = 12$$ valence electrons
- O: 2 × 6 electrons
Step 24:: Draw Lewis structure
O \equiv O
- Double bond between O atoms (i) HBr (Hydrogen bromide)
Step 25:: Draw Lewis structure
H - Br:
- Single bond between H and Br - Three lone pairs on Br
Final Answer
Lewis structures have been drawn for each molecule/ion, following the octet rule and showing all valence electrons.
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