intermolecular bonds Flashcards
Why are intermolecular forces present
In a liquid or solid there must be forces between the molecules causing them to be attracted to one another, otherwise, the molecules would move apart and become gas
Define intermolecular Force
a weak force of attraction between molecules, ions, or atoms of noble gases
What is a dipole-dipole force
attractive forces between polar molecules. The positive end of one polar molecule and the negative end of another polar molecule are attracted to each other
London Forces
intermolecular forces between non polar molecules. This occurs temporary dipole is forced between the molecules
All interactions between particles involve some sort of London forces
How does the strength of a London force depend on the size of the molecules
-As the molecules increase in size the strength of the intermolecular forces increase
-The Larger molecules have more electrons which results in greater electron density and grater interactive surface
- which result in larger temporary dipoles which last longer
Hydrogen Bonding Forces
H- bonds occur between molecules which conatin hydrogen bonded with nitrogen, oxygen or fluorine (NOF)
Stronger than normal dipole dipole forces
What are the Characteristics of H-Bonds
bonded to-
small atoms
large electronegativity difference between the atoms within the molecule
The atom bonding to the hydrogen has at least one lone pair of electrons
Why do Network Solids such as diamond, graphite and silicon dioxide have high melting and boiling points
large amount amount of energy needed to break the many strong covalent bonds
What are the properties of Ionic solids
Fixed position and form an ionic lattice
- high melting and boiling points
- Hard and brittle
- Does not conduct electricity on solid phase
- The melting and boiling points of ionic solids are dteremined bye electrostatic forces of attractions (ionic Bonds) between the cations and anions
Why are metals good conductors
Valence electrons are free to move from one atom to the next. These electrons are delocalized and do not belong to a specific atom but rather a entire metal lattice.
Metals are good conductors of electricity in soild and liquid state due to these free electrons
When can Ionic compounds conduct electricity
molten or liquid phase as the ions are free to move
Why is Graphite a good conductor
fourth Valence electron being delocalised
Why dont diamond, silicon and silicon dioxide conduct electricity
all valence electrons in the structure are bonded
What is the diifference in melting and boiling points for H-bonbs
the difference is due to the relative number of hydrogen bonds that occur between the particles . The more sites for Hydrogen bodning to occur the higher the melting and boiling points
What is the difference in melting and boiling points of substances in the same group on the periodic table 4
The difference is due to the london forces between the molecules
