Question

why is the structure either not important or less important? select the single best answer.
:o≡c—ö:
not important (octet rule violated)
less important (negative formal charge on carbon)
less important (positive formal charge on oxygen)
not important (wrong number of electrons)

Explanation:

• Octet rule: The octet rule states that atoms tend to gain, lose, or share electrons to have 8 electrons in their valence shell. In the given structure, each atom (O, C, O) has 8 electrons around it (counting bonding and non - bonding electrons). So, the octet rule is not violated.
• Formal charge formula: The formal charge formula is \(FC = V - N-\frac{B}{2}\), where \(V\) is the number of valence electrons, \(N\) is the number of non - bonding electrons, and \(B\) is the number of bonding electrons.
• For the left - hand \(O\): \(V = 6\), \(N = 2\), \(B = 6\). \(FC=6 - 2-\frac{6}{2}=1\) (positive formal charge).
• For \(C\): \(V = 4\), \(N = 0\), \(B = 8\). \(FC = 4-0-\frac{8}{2}=0\).
• For the right - hand \(O\): \(V = 6\), \(N = 6\), \(B = 2\). \(FC=6 - 6-\frac{2}{2}=-1\).
• Electron count: The total number of valence electrons in \(CO_2\) is \(4+(6\times2)=16\). In the given structure, the number of electrons (counting bonding and non - bonding) is also \(16\) (\(2\times6 + 4=16\)).

Since oxygen is more electronegative than carbon, a structure with a positive formal charge on oxygen (more electronegative atom) is less stable (less important) compared to a structure where the formal charges are more in line with electronegativity trends.

Answer:

less important (positive formal charge on oxygen)