bond polarity and intermolecular forces Flashcards
What is electronegativity?
The power of an atom to attract the shared pair of electrons
What happens to electronegativity across a period and why?
Increases because there are more protons ,the same shielding and atomic radius decreases.
What happens to electronegativity down a group?
Decreases because there is more shielding so there is less attraction for the shared pair of electrons.
What elements have the highest and the lowest electronegativity?
Fluorine-highest
caesium-lowest
What is a polar covalent bond ?
Unequal sharing of a bonding electron pair as the electron distribution is unsymmetrical.
What is a bond purely covalent?
There is little to no difference in electronegativity.
Why is co2 a non polar molecule despite having polar bonds?
The dipoles cancel out as the electrons are evenly distributed.
What does permanent dipole-dipole forces occur between?
Polar molecules e.g. the hydrogen halides ( HCL , HBr, HI)
How do dipole-dipole forces arise ?
One element is more electronegative so the shared pair of electrons is more attracted towards it creating a permanent dipole within the molecule one is slightly + one is slightly negative.
Where do vanderwaal forces exist ?
Between all molecules and is the weakest intermolecular force.
How do vanderwaal forces arise?
At any moment there may be more electrons on one side of the molecule than the other creating a temporary dipole which causes a dipole on an adjacent molecule (induced dipole) so the molecules attract.
How does the size of the molecule affect the strength of the force?
The bigger the molecule the stronger the Van der waal forces between the molecules.
Where do hydrogen bonds exist?
Between molecules with F-H or O-H or N-H bond
The melting and boiling points of molecular substances are influenced by the strength of these intermolecular forces.
The importance of hydrogen bonding in the low density of ice and the anomalous boiling points of compounds.
