What is wrong with the Lewis structure shown for sulfur trioxide, SO3? Multiple Choice Oxygen, not sulfur, should be the central atom. 0 The structure should show each oxygen atom with a double bond to the sulfur atom. There are too many bonding electrons shown. O Sulfur should have 10 electrons around it instead of 8, to show its expanded octet. The structure shows 26 valence electrons, but there should only be 24.
The Correct Answer and Explanation is :
The correct answer is: The structure shows 26 valence electrons, but there should only be 24.
Explanation:
The Lewis structure for sulfur trioxide (SO₃) must reflect the correct number of valence electrons and bonding patterns according to sulfur and oxygen’s electron configurations. Let’s break it down:
- Valence Electrons:
- Sulfur (S) is in Group 16, so it has 6 valence electrons.
- Oxygen (O) is also in Group 16, so each oxygen atom has 6 valence electrons. Since there are three oxygen atoms, that contributes 18 electrons (6 × 3).
- Adding the electrons from sulfur and oxygen, the total number of valence electrons in SO₃ is 24 (6 + 18).
- The Octet Rule:
Oxygen atoms tend to form bonds in such a way that they have 8 electrons in their outer shell (octet rule). However, sulfur can have an expanded octet because it is in the third period and can accommodate more than 8 electrons. In the correct structure, sulfur has 12 electrons around it (three double bonds, with each oxygen atom sharing two electrons), which follows sulfur’s ability to exceed the octet rule. - Common Errors:
The incorrect Lewis structure in this question shows 26 valence electrons instead of the correct 24. This might arise from an attempt to form an extra bond or by adding lone pairs incorrectly. Sulfur does not need 10 electrons to form its bonds; it forms double bonds with each oxygen, and the total number of bonding and lone-pair electrons should be carefully counted to match the 24 valence electrons. - Correct Structure:
In the correct structure, sulfur forms a double bond with each of the three oxygen atoms. This satisfies both the expanded octet for sulfur (12 electrons) and the octet for each oxygen atom, using the correct number of 24 valence electrons.
Understanding this correct distribution is crucial for drawing proper Lewis structures in chemistry.