2.7 Flashcards
(31 cards)
What does VSEPR stand for?
Valence Shell Electron Pair Repulsion
VSEPR theory helps to describe the 3D shape of molecules.
Who co-created the VSEPR theory?
Ronald Gillespie and Ronald Nyholm
The theory was developed in 1957.
What limitation does the Lewis theory of bonding have?
It only shows molecules and ions in 2D
Lewis structures do not represent the three-dimensional shapes of molecules.
What is the primary idea behind VSEPR theory?
Electrons will maximize the amount of 3D space between them
This is due to the repulsion between negatively charged electrons.
Which has greater repulsion according to VSEPR theory?
Lone pairs inflict greater repulsion than bonded pairs
This affects the geometry of the molecule.
What does ‘A’ represent in the VSEPR notation AXnEm?
The central atom
It is the atom with the most bonding electrons.
What does ‘X’ denote in the VSEPR notation AXnEm?
An atom bonded to the central atom
This can include single, double, or triple bonds.
In the notation AXnEm, what does ‘n’ represent?
The number of atoms bonded to the central atom
It indicates how many X atoms are connected to A.
What does ‘E’ signify in the VSEPR notation AXnEm?
The lone pairs on the central atom
This helps determine the overall molecular geometry.
In the notation AXnEm, what does ‘m’ indicate?
The number of lone pairs on the central atom
This is crucial for predicting the shape of the molecule.
What is the 3D geometry for a molecule with 3 electron regions and no lone pairs?
Linear
This applies when there are no lone pairs affecting the geometry.
What is the 3D geometry for a molecule with 4 electron regions and 1 lone pair?
Trigonal pyramid
The lone pair alters the shape from tetrahedral.
What is the bond angle in a trigonal planar geometry?
<120°
This angle is a result of electron pair repulsion.
What is the 3D geometry for a molecule with 5 electron regions and 2 lone pairs?
T-shaped
The presence of lone pairs affects the geometry significantly.
What is the bond angle in an octahedral geometry?
90°
This is typical for structures with 6 bonded regions.
Fill in the blank: The notation AXnEm helps to determine the _______ geometry.
3D
Understanding the notation is essential for visualizing molecular shapes.
What do solid wedges represent in a 3D molecular structure?
Atom(s)/pairs of electrons coming towards the viewer.
What do dashed wedges represent in a 3D molecular structure?
Atom(s)/pairs of electrons going away from the viewer.
Where do we include lone pair electrons in a molecular structure?
Only on the central atom.
What is the first step to drawing VSEPR structures?
Draw the Lewis structure for the molecule.
What do you need to include in the Lewis structure around the central atom?
The electron pairs.
How do you write the VSEPR notation of the central atom?
By counting the total number of bonded atoms and lone pairs of electrons around the central atom.
What does the VSEPR notation help to predict?
The shape of the molecule.
What is the procedure for polyatomic ions regarding formal charges?
Do not include the formal charges on individual atoms; instead, put square brackets around the 3D shape and write the overall charge on the top right.
