# 124 problems for slides and class for each of the

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124 Problems for slides and class For each of the following groups, place the atoms and/or ions in order of decreasing size . Cu, Cu + , Cu +2 Ni +2 , Pd +2 , Pt +2 O, O -1 , O -2 La +3 , Eu +3 , Gd +3 , Yb +3 Te -2 , I -1 , Cs +1 , Ba +2 , La +3
125 Problems for slides and class For each of the following groups, place the atoms and/or ions in order of decreasing size . Cu, Cu + , Cu +2 Cu > Cu + > Cu +2 Ni +2 , Pd +2 , Pt +2 Pt +2 > Pd +2 > Ni +2 O, O -1 , O -2 O < O -1 < O -2 La +3 , Eu +3 , Gd +3 , Yb +3 La +3 > Eu +3 > Gd +3 > Yb +3 Te -2 , I -1 , Cs +1 , Ba +2 , La +3 Te -2 > I -1 > Cs +1 > Ba +2 > La +3
126 End Chapter 9
127 Lewis electron-dot symbols for elements in Periods 2 and 3.
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129 Valence Shell Electron-Pair Repulsion (VSEPR) model Molecular geometry is the name of the geometry used to describe the shape of a molecule. The five basic shapes you must know The electron-pair geometry provides a guide to the bond angles of between a terminal-central-terminal atom in a compound. The molecular geometry is the shape of the molecule. The 13 possible shape a molecule will have
130 Valence Shell Electron-Pair Repulsion (VSEPR) model After being familiar with Lewis structures most instructors go on to VSEPR. I do them both at the same time. At this point we are ready to explore the three dimensional structure of simple molecular (covalent) compounds and polyatomic ions. We will use a model called the Valence Shell Electron-Pair Repulsion (VSEPR) model that is based on the repulsive behavior of electron-pairs. This model is fairly powerful in its predictive capacity. To use the model we will have to memorize a collection of information.
131 Covalent Bonding and Lewis Structures Writing Lewis Structures Sum the valence e- from all atoms Choose the central atom Here are some VSEPR animations that do not require a plug-in to view.
132 Covalent Bonding and Lewis Structures Writing Lewis Structures Choosing the Central Atom Least electronegative atom goes in center. The largest atom is the central atom most often. Usually the first element listed is the central atom with the exception of hydrogen. Exceptions H 2 O and others You can have only 1 central atom Examples Simple at first
133 Covalent Bonding and Lewis Structures Writing Lewis Structures Use a pair of e- to form a bond between each pair of bonded atoms arrange the remaining e- to satisfy the duet and octet rules. This may mean double or triple bonds
134 Covalent Bonding and Lewis Structures Writing Lewis Structures Sum the valence e- from all atoms. Choose the central atom, see below. Draw a skeleton structure, only single bonds at first. Use a pair of e- to form a bond between each pair of bonded atoms Arrange the remaining e- to satisfy the duet and octet rules. This may mean double or triple bonds. Do not forget the possibility of resonance.
135 Covalent Bonding and Lewis Structures Choosing the Central Atom Least electronegative atom goes in center.