VSEPR Theory Flashcards
What is an electron group?
A set of electrons that occupies a particular region around an atom. Examples: lone pairs, bonds
What term describes how the ligands of a molecule, as opposed to the electron groups, are arranged in a molecule?
Molecular shape
What are the possible molecular shapes of a molecule with tetrahedral electron group geometry?
Tetrahedral, trigonal pyramidal, and bent.
How is the steric number determined?
Number of ligands + number of lone pairs
Describe the four steps to determining molecular shape.
Lewis structure
Steric number
Electron group geometry
Ligand count
What is electron group geometry?
The three-dimensional arrangement of valence shell electron groups.
What is the ideal bond angle for a molecule with linear shape and geometry?
180*
What is the steric number and ideal bond angle for a molecule with trigonal planar shape and electron group geometry?
3; 120*
What is the electron group geometry of a molecule with steric number 5?
Trigonal bipyramidal
Give the ideal bond angle(s) of a molecule that has trigonal bipyramidal electron group geometry.
120* between equatorial positions; 90* between axial positions.
A molecule has 5 electron groups, and one of them is a lone pair. Give the two possible molecular shapes.
Trigonal pyramid
Seesaw
A molecule with octahedral electron geometry can have up to two lone pairs. Give the three possible molecular shapes.
Octahedral
Square pyramidal
Square planar
The bond angles of a molecule are all 109.5*. Give the electron group geometry.
Tetrahedral
True or false: lone pairs repel other electron groups less strongly than those groups repel each other.
Why?
False. Electrons in a lone pair are more strongly attracted to their nucleus than bonding electrons.
What are the key factors in determining the dipole moment of a molecule?
Electronegativity differences and molecular geometry.
How would you compare two bond lengths without knowing the measurements?
Look at the atomic radii, then the presence of multiple bonds, then the nuclear charges, then electronegativity differences.
Which steric number has 4 possible molecular shapes?
5
What is the term for the number of ligands in a molecule?
Coordination number
