Night Before the Test

     I feel like I have prepared well for the test because I have reviewed notes and completeted the practice tests and worksheets available for test prep online. I feel like I am extra worried about this test because there is no quiz, so this test will make an even larger impact on my grade. I feel like tomorrow should not be that bad though. Hopefully I am not proved wrong.

For those still needing to study, check out the links below:

• Formal charge practice
• Drawing lewis dot structures
• Resonance structures
• Molecular shape and geometry
• Molecular shape and geometry practice quiz
• Bond polarity

Bond Polarity

     When a bond between 2 or more elements is formed, there may be a slight pull of the electrons in the bond toward the more electronegative element which results in a polar molecule. Today we learned how to determine whether or not a bond is polar.

     In the molecule above, flourine (F) has the greatest electronegativity which can be found on the periodic table. Because of this, the electrons are pulled toward it and cause an unequal distribution of charge. F has a slightly negative charge as noted by delta minus because is has to negatively charged electrons closer to it. This unequal distribution in charge causes a dipole moment, which is represented by the arrow above the molecule as shown above, The dipole moment points towards the more electronegative atom. In a molecule containing a single bond is automatically polar if it has a dipole moment, like the HF molecule shown above. Dipole moments do not always mean polar in molecules involving multiple bonds, however.

     For example, the CO2 molecule contains dipole moments but is not considered polar. The oxygens are the more electronegative atoms, so the dipoles point outwards. These 2 dipoles are in the completely opposite directions, so they cancel each other out, making the molecule nonpolar. 

Modeling Lab in Library

Shown above is the HNS, lewis dot structure, and 3D molecule SF4

     Today our class met in the library to do an activty that would help us better understand how to draw lewis dot structures using the have need share model and how to buid these molecules in 3D. Also, this lab gave us practice with determining the shape and geometry of a molecule. I enjoyed this activty because I like working hands on and getting to use the dry erase tables was fun. I am happy we did this lab toward the beginning of the unit because it really helped us get the basics down before moving onto more difficult concepts.