In this unit we will begin looking at how the electron configuration of elements plays a role in the types of compounds it forms.
LEARNING TARGET #1 - Draw an Electron Dot Diagram for any element.
We began with creating Lewis Dot diagrams for each element. Notice the rules about drawing electron dot structures. You always fill one orbital before pairing them up - in other words, you draw one electron (dot) on the side, top, other side and then bottom before putting a second electron in a pair. What element do you first see a pair of electrons in the picture below? You should have answered N. Helium is often drawn as a pair of electrons since the first electron shell only holds two electrons. Notice that with Lithium we only draw one electron. This is because it only has one electron in its outermost shell. Lithium's electron configuration is 1s2 2s1 - the 2 is the outermost shell and it only has one electron. This is how we do it for every element. Note that transition elements will for these purposes show a valence number of 2 because the D block is always lower than the S block -so D electrons are never valence electrons.
LEARNING TARGET #2- Use the electron dot diagrams to determine chemical compounds.
Using the electron dot diagrams, you can determine how many bonds an element will typically form. For example, because H has only 1 unpaired electron, it typically only forms a single bond. Carbon, on the other hand, has 4 unpaired electrons and it will typically form 4 bonds with other atoms. Neon, a noble gas, has 4 pairs of electrons - or a complete octet - so it tends to not form any bonds. This is why the noble gases are essentially non-reactive. Their outermost - or valence - shell of electrons is already filled.
In the example below, Cl has only 1 unpaired electron so it will form only a single bond. Carbon, has 4 unpaired so it will need to form 4 bonds to be stable. So how many Cl atoms would we need to bind to C to make it stable? You should have said 4!
This is what it would look like with 4 Cl atoms around it.
Then, the electrons that are shared between two atoms get represented as a single line like this:
Learn more about making Lewis Structures with this video tutorials here: