Lewis Diagrams for Atoms
Generally the electrons that will be involved in bonding (of whatever kind) will be the
valence electrons. These are the electrons on the outer perimeter of an atom. The number
of valence electrons for an atom is often, but not always, determined from the position of
that element on the periodic table.
|A handy way to illustrate these valence electrons is to use Lewis
diagrams, also called electron dot diagrams. These diagrams show the symbol of the element
with as many dots around it as there are electrons in the outermost energy level. For
example, boron with its electron configuration of 1s22s22p1
has three valence electrons and the Lewis diagram is the symbol B with three dots around
it, representing those three valence electrons. Lewis diagrams are useful and easy to draw
for the representative elements, which are the Group I-A and II-A metals and the
nonmetals. However, because of the overlapping energy sublevels, these electron dot
diagrams become useless for the transition metals, so we won't bother with Lewis diagrams
I'd like you to get some practice by drawing electron dot diagrams for these elements
now (or by doing exercise 1 in your workbook).
Let's go through those quickly. You should have had only one real problem. As you can
see, sodium has one dot and magnesium has two. Iron is the problem. It is a transition
metal so we will not deal with it. Arsenic has five. Fluorine has seven. Neon has eight.
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