E L L A R O Y
Portfolio 2015/2016
Grade 10
Molecular Structures and Geometry
Unit overview
For students to learn the properties and rules of or molecular structures. They will use their knowledge in chemical bonding to draw Lewis Structures of the molecular compounds. The students will then be able to determine the molecular geometry of the compound from the Lewis Structure.
Personal Unit Overview: What did you achieve this unit?
I feel like what I did best this unit was understanding how to draw Lewis structures.
Enduring Understandings: Chemical Bonding
There are three main types of chemical bonding. The first one is ionic bonding, which is when atoms ‘give and take’ electrons (the attraction between (cat- and an-ions). Ionic bonds occur between nonmetals and metals. Covalent bonds however are between nonmetals and nonmetals where the pair of valence electrons are shared by atoms. If they are equally shared, the bond is nonpolar covalent, while polar covalent bonding is when a pair of electrons is unequally shared. Lastly, there are metallic bonds that occur between metals. The key phrase to this bond is ‘a sea of electrons’, as all the valence electrons are ‘delocalised’.
Lewis Structures
1. Find the total number of valence electrons
a. Add all the valence electrons from each element
2. Find the number of electrons needed to make the atom
“happy” (octet rule)
a. Remember how many electrons each element needs to
be stable
3. Determine the number of bonds in the molecule
a. Take the total number needed to make the molecule
“happy” and subtract the total number that the molecule
has then divide that by two since a bond consists of two
electrons (step 2 – step 1)/2
4. Choose a central atom
a. This is the one that is least electronegative (with the
exception of Carbon). Remember Group 1 least
electronegative – Group 17 most electronegative. Also
remember that hydrogen is usually on the outside.
5. Draw the skeletal structure
a. Connect the atoms to the central atom with the bond line
6. Place the electrons around the outside atoms
a. Complete your octets
7. Place the remaining electrons around the central atom
a. Complete Octet rule for central atom with remaining
electrons. If there are bonds left over from Step 3, create
multiple bonds.
Identifying the structure
Reflection on Standards
Strength
Demonstrates the understanding of chemical bonds.
Explanation
I was quickly capable of understanding and remembering the three types of chemical bonds we studied, as well as their properties and how each bond occurs.
Weakness
Develops reading literacy in Science
Explanation
Reading literacy in science is something I find quite difficult as I lack the vocabulary to understand most things. To improve this during the next unit, I could try reading more which would also improve my scientific writing.
