We’re being asked to identify the compound that it is necessary to use an expanded octet to represent a Lewis structure that has zero formal charges on the central atom.
Recall that the octet rule states that an element is surrounded by eight electrons in the Lewis structure.
Exceptions to this rule occur when:
• there is an odd number of electrons, like in radicals
• there are less than 8 electrons or incomplete octet
• there are more than 8 electrons or expanded octet. This occurs to nonmetals from Period 3 to 7.
For this problem, we need to draw the Lewis structure for each compound.
To do so, we need the following steps:
Step 1: Determine the central atom in this molecule.
Step 2: Calculate the total number of valence electrons present.
Step 3: Draw the Lewis structure for the molecule.
1. In which of the following is it necessary to use an expanded octet to represent a Lewis structure that has zero formal charges on the central atom?
A) SiCl2F2 ;
B) SO4 2− ;
C) CO32− ;
D) PO43− ;
A. D and E only
B. A and B only
C. E only
D. C, D, and E only
E. B, D, and E only
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