Chemistry CN Chemist:_______________ Date:_____________ Period:_____ Topic:________________________________________________________________________ Remember: In a Lewis Structure: Only the ______________________ are involved Most atoms strive to get 8 e- in their outer principal electron layer. This is the “_________________.” Each ______________represents 1 electron. Each ______________ represents 2 shared electrons in a ___________________ bond. Sometimes the lines are shown as dots How to draw Lewis Structure for the 1. Count the valence e- available. _________ electrons for negative charges. OCl- (bleach) ion. __________ electrons for positive charges 2. Draw a “skeleton” structure using single bonds (lines) for pairs of shared electrons. 3. Distribute the rest of the e- around the atoms so each atom has ____ electrons. There are 3 things that can occur with your electrons on the central atom: Important Tips: 1. There are just enough e- to go around. Every atom has ______and H atoms have _______. 2. If there aren’t enough e- to go around, then move a pair of e- next to an existing single bond to make a double or triple bond. 3. If there are too many e-, then the atom may have an “____________________.” Put the extra e- pairs on the central atom. ___________ is usually a central atom, while H, O, and the __________ are usually terminal atoms with ONLY one single bond. Chemistry CN Chemist:_______________ Date:_____________ Period:_____ Topic:________________________________________________________________________ The__________ atom listed in the chemical formula is usually the central atom. Carbon always has 4 lines (4 covalent bonds) coming off of it. Draw the Lewis Structure for CH3OH, methanol. Draw the Lewis Structure for the sulfite ion, SO32- Draw the Lewis Structure for the Nitrate ion, NO3- Exceptions to the Octet Rule: Part 2: Predicting Molecular Geometry (Shapes) Some _______________ elements don’t have 8 e- on the central atom. Examples: Molecular shapes can be predicted using the Valence Shell Electron Pair Repulsion, ______________ principle. All e- pairs try to get as ______________________ from each other as possible. You must draw the Lewis structure before you can predict the geometry. Add up the number of “________________” pushing away from the central atom. (continued) Chemistry CN Chemist:_______________ Date:_____________ Period:_____ Topic:________________________________________________________________________ Each ___________________________ and atom(s) bonded to the central atom, count as a “force.” Double or Triple bonds behave like just ______“force.” The 3 basic “Repulsion Angles” 2 Forces: make a _______________ molecule with _______ angles off the central atom. 3 Forces: repel in a _______________ pattern with _______ angles. 4 Forces: repel in a ________________ pattern with _________ angles. How do you tell if a molecule is “polar?” What is the molecular geometry of A molecule is “___________________” when it has more electrons on one side than on the other. This means it has a negative side with more electrons and a positive side with less electrons. Generally, if a molecule is perfectly ________________with no unshared e- pairs, then it is non-polar. __________________ usually make it polar. If the ____________________ are different, then it's polar (different charge on each end) BF3 ? Geometry: Angle(s): Polar/nonpolar: What is the geometry of a water Geometry: molecule? Angle(s): Polar/nonpolar: Chemistry CN Chemist:_______________ Date:_____________ Period:_____ Topic:________________________________________________________________________ Summary: (3-4 GOOD sentences) On separate sheet of paper.