Shapes Of Molecules And IMF Flashcards
What is a valence shell?
The outer shell
What are lone electron pairs?
Two electrons that are not involved in a Bond
What is the valence shell electron pair repulsion theory?
Pairs of electrons in valence shell repel each other as far as possible
Multiple bonds have same effect as single bonds
Lone pair of electrons have larger repelling effect than bonded electrons (more lone electrons= reduces bond angle)
How do you determine the shape of a molecule and bond angles?
Draw dot and cross diagram
Take into account repelling effects of bonds
What is the shape and bond angle of a molecule with 2 bonded pair of electrons/ regions?
Linear
180
What is the shape and bond angle of a molecule with 3 bonded pair of electrons/ regions?
Trigonal planar
120
What is the shape and bond angle of a molecule with 4 bonded pair of electrons/ regions?
Tetrahedral
109.5
What is the shape and bond angle of a molecule with 6 bonded pair of electrons/ regions?
Octahedral
90
What is a dative bond?
A covalent bond where nth electrons come from the same atom
What does the triangle in a dot and cross diagram signify?
+ when is it used?
Used in poly atomic ions
To signify electrons gained
What is a covalent bond?
The attraction between the positive nucleus of two atoms and the negative electrons they share .
What is electronegetivity?
The ability of an atom to attract the bonded pair of electrons in a covalent
What are the electronegativity values called?
Pauling electronegativity values
What is the most electronegative atom?
Fluorine
What is a polar bond ?
A covalent bond where each atom has different electronegativities with + and - partially charges on the atoms
Will the more electronegative atom has a + or - partial charge?
Partial negative charge
What is a dipole?
The separation (short distance) of partial charges in a molecule
What is a permanent dipole?
The separation of partial charges across a polar bond due to different electronegativities
When is molecule polar?
When a molecule has more than one polar bond and is not symmetrical
Why are some molecules non-polar even though they have 2+ polar bonds?
The molecule is symmetrical so the dipole acts in opposite directions and cancels out
What are intermolecular forces?
Weak attraction between molecules
What are the types of intermolecular forces?
Induced dipole-dipole attraction (London forces)
Permanent dipole-dipole interactions
Hydrogen bonding
What are temporary dipoles and why do they form?
Dipoles caused by uneven distribution of electrons
Form due to random nature of electron movement
What is an induced dipole and how is it created?
A dipole caused by the presence of a temporary dipole in a molecule
Chain reaction
What is a London force?
The force of attraction between induced dipoles
Where do London forces occur?
In all molecules
What does the head of an arrow indicate in terms of dipoles?
Partial negative charge