Modeling Molecules 4.9

This activity asks you to represent a molecule as a chemical formula, electron dot structure, structural formula, and as a 3D drawing.

Example: Propionic acid, a food preservative

• Chemical Formula (aka Molecular Formula): Indicates the number of each atom in the compound, but does not give any indication of the bonds or shape of the compound. o Example: The chemical formula of Propionic acid is C3H6O2. The only information that is given in this formula is that the compound has 3 Carbon atoms, 6 Hydrogen atoms, and 2 Oxygen atoms. There is no information about how these atoms are arranged. . To find the Chemical Formula, open Google search and type in “chemical formula for ______” This returns the chemical formula for your compound. 1. Example: Propionic Acid

Type into the Google Search bar

Find out the Chemical Formula

• Electron Dot Structure: use dots to show the bonding electrons and lone pair electrons in a compound. o Remember, atoms can only donate their valence electrons to a bond and most elements with atomic numbers less than 20 follow the octet rule. One notable exception is Hydrogen which only forms a duet (2 electrons). . I highly encourage you to go to this website and practice these structures: http://www.wisc- online.com/objects/ViewObject.aspx?ID=GCH6404 . You should make drawings of the Electron Dot Structures, take pictures with a digital camera or cell phone camera, and submit them as picture uploads. o Example: Propionic acid

• Structural Formula: Represents covalent bonds as dashes and shows the arrangement of covalently bonded atoms. o The Structural Formula is very similar to the Electron Dot Structure, but it only represents the valence electrons which are participating in the bond. o Example: Propionic acid

• 3D drawing o Although the Portfolio instructions direct you to make models of each of these molecules (Steps 3 and 4), the important thing is not that you create the model itself, rather that you have the opportunity to observe the molecule as a 3-dimensional figure. The lesson directs you to a very cool website (http://molview.org/?cid=5234) which generates 3D versions of each of the assigned molecules. You can use these 3D models to make your drawing, which can then be submitted by any appropriate means (scanning, fax, picture upload, etc.). . Color key 1. Carbon: Gray 2. Hydrogen: White 3. Oxygen: Red 4. Sulfer: Yellow 5. Chlorine: Green o Make sure you identify each atom in the molecule either by providing a key, or by individually labeling each one. o EXAMPLE: Propionic acid Key O H Carbon (C)= Gray Hydrogen (H)= White C C Oxygen (O)= Red H H O H C H

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