Three lone pairs of electrons are placed around each F atom, accounting for 12 electrons and giving each F atom 8 electrons.
The lone pairs have to be placed on the Xe atom.
The Lewis structure of XeF2 shows two bonding pairs and three lone pairs of electrons around the Xe atom.
The interhalogens are a class of compounds in which the halogens bond to each other.
In the previous section, we talked about how to write Lewis structures.
In some cases, there is more than one valid structure for a molecule.
When more than one is reasonable, we can use the concept of formal charges to predict the most appropriate Lewis structure.
When we take the number of electrons of a neutral atom, subtract the nonbonding electrons, and then subtract the number of bonds connected to that atom in the Lewis structure, we can say that formal charge results.
The sum of the formal charges for the whole structure can be double checked.
The sum of the formal charges of all atoms in a molecule must be zero, and the sum of the formal charges in an ion must be equal to the charge of the ion.
The formal charge does not indicate the presence of actual charges.
The I atom has eight electrons and the Cl atom has seven.
The charge of the ion is the same as the charge of the atoms.
Each atom has seven electrons.
A neutral molecule has a formal charge of zero and the sum of it's formal charges totals zero.
Determine the formal charge for each atom.
The steps for writing Lewis structures can lead to more than one possible structure, such as a different multiple bond and lone-pair electron placement.
A structure in which all formal charges are zero is better than one in which some charges are not zero.
The arrangement with the smallest nonzero formal charges is preferable if the Lewis structure has nonzero formal charges.
Lewis structures are better if the charges are zero or the opposite sign.
The structure with the negative formal charges on the more electronegative atoms is preferable when we must choose among several Lewis structures with similar distributions of formal charges.
Let's look at some possible structures for carbon dioxide, CO2.
The structure on the left has only formal charges of zero so we can conclude that it is preferable.
A carbon atom, a nitrogen atom, and a sulfur atom can make up the thiocyanate ion.
The formal charges present in each structure can help us pick the most likely arrangement of atoms.
The charge of the ion is equal to the sum of the formal charges in each case.
The first arrangement of atoms has the lowest number of atoms with no formal charges.
The negative charge on the more electronegative element is placed in the center.
The laughing gas, N2O, is used as an anesthesia in minor surgeries, such as the routine removal of wisdom teeth.
There is no formal charge larger than one for the number of atoms with formal charges.
This is consistent with the preference for a less negative atom in the central position.
We would expect the two bond lengths to be different if there is a single and a double bond.
A double bond between two atoms is stronger than a single bond between the same two atoms.
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