Chapter 9 Molecular Geometry Full Analysis
What properties of molecular substance depend on? - The structure of the molecules
The structure
... [Show More] includes many factors: - -The skeletal arrangement of the atoms
-The kind of bonding between the atoms
-The shape of the molecule
Bonding theory should allow what? - To predict the shapes of molecules.
Molecules - are three-dimensional objects
How do we describe the geometric figures? - The shape of a molecule with terms that relate to geometric figures
Bond angles - The geometric figures also have characteristic angles
What does Lewis theory predicts? - There are regions of electrons in an atom and the number of valence electrons pairs around the central atom(s)
What does Lewis theory says about these regions of electron groups? - That these regions of electron groups should repel each other, because they are regions of negative charge
Valence shell electron pair repulsion theory - Electron groups around the central atom will be most stable when they are as far apart as possible.
Why electrons need to be far apart as possible? - Because electrons are negatively charged, they should be most stable when they are separated as much as possible.
How much each lone pair of electrons constitutes electron group on a central atom? - One electron group
How many basic arrangements of electron groups around a central atom - Five
Linear geometry - When there are two electron groups around the central atom, they will occupy positions on opposite sides of the central atom. The bond angle is 180 degrees.
Trigonal planar geometry - When there are three electron groups around the central atom, they will occupy positions in the shape of a triangle around the central atom. The bond angle is 120 degrees
Tetrahedral geometry - When there are four electron groups around the central atom, they will occupy positions in the shape of a tetrahedron around the central atom. The bond angle is 109.5 degrees.
Trigonal bipyramidal geometry - When there are five electron groups around the central atom, they will occupy positions in the shape of two tetrahedral that are base to base with the central atom in the center of the shared bases. The bond angle between equatorial positions
is 120°. The bond angle between
axial and equatorial
positions is 90 degrees. [Show Less]