Which of the following is the
correct Lewis structure for a fluoride ion?
The first step in creating our
Lewis structure is to write the appropriate atomic symbol. We need to create a Lewis structure
for a fluoride ion. Fluoride ions are an ion of the
element fluorine, which has the atomic symbol F. Next, we need to determine the
number of valence electrons. Fluorine is in group seven of the
periodic table. Fluorine, like the other elements
in group seven, have seven valence electrons. When the atoms of elements in group
seven form ions, they tend to gain one electron. This forms an ion with a charge of
negative one and gives the ion a full valence shell. So we know the fluoride ion has
eight valence electrons.
Now that we know the number of
valence electrons, we’ll place a number of dots equal to the number of valence
electrons around the atomic symbol. We can place two dots on each side
of the atomic symbol until we’ve used up all of the valence electrons. And now, because we’re creating the
Lewis structure for an ion, we have one more step. We need to surround our Lewis
structure with square brackets and indicate the charge of the ion in the top-right
corner. As we can see, the Lewis structure
we’ve created for a fluoride ion matches the structure in answer choice (E).