Decide whether these proposed Lewis structures are reasonable.

Question: Decide whether these proposed Lewis structures are reasonable.

Proposed structures :

1. H — H — O with two lone electrons on O
2. :F = O = F: with lone pairs on the fluorines
3. [H — H — O — H]^+ (with O presumably having no lone pairs)

Answer: 1. No, it has the right number of valence electrons but doesn't satisfy the octet rule.

The symbols of the problem atoms are: O

Answer: 2. No, it has the right number of valence electrons but doesn't satisfy the octet rule.

The symbols of the problem atoms are: F, F (for both fluorine atoms)

Answer: 3. No, it has the right number of valence electrons but doesn't satisfy the octet rule.

The symbols of the problem atoms are: O

Explanation:

Step1: Determine total valence electrons

1. For H₂O: H (1 e⁻) × 2 = 2 e⁻; O (6 e⁻) = 6 e⁻; total = 8 e⁻.
2. For OF₂: O (6 e⁻) + F (7 e⁻) × 2 = 6 + 14 = 20 e⁻.
3. For H₃O⁺: H (1 e⁻) × 3 = 3 e⁻; O (6 e⁻) = 6 e⁻; total before charge = 9 e⁻. With a +1 charge, total valence electrons = 8 e⁻.

Step2: Apply the octet rule

1. H — H — O: The oxygen ends up with only three pairs of electrons (one bonding pair and two lone pairs = 6 electrons), not 8. O is not satisfying the octet rule.
2. :F = O = F:: Typically, fluorine forms only single bonds and holds three lone pairs to complete its octet. Double bonding to oxygen would force F out of its normal valence structure. Thus, F atoms do not have a proper octet configuration here.
3. [H — H — O — H]^+: Oxygen is bonded to three hydrogens. With three bonds (6 electrons) and no lone pairs, O ends up with only 6 electrons. Even though the total electron count is correct for the charged species, the octet rule is not satisfied for O.

Extended Knowledge:

Octet Rule Basics

The octet rule states that most atoms in stable molecules aim to have eight electrons in their valence shell. This is commonly seen with second-period elements like C, N, O, and F. Hydrogen is an exception, requiring only 2 electrons.

Common Bonding Patterns

• Oxygen typically forms two bonds and has two lone pairs, ensuring it reaches an octet (8 valence electrons around it).
• Fluorine almost always forms a single bond and has three lone pairs to maintain its octet.
• Charged species (ions) must also respect these electron distribution rules. When dealing with ions, you must adjust the total valence electron count accordingly and still ensure that central atoms like O meet their octet requirements unless exceptions apply.