Electrons, Bonding adn Strucutre part 2 Flashcards
What is a temporary dipole
a separation of charge caused by the random movement of negative electrons around the positive nucleus
what is an induced dipole
a separation of charge caused by a nearby dipole
what is a London force
attractive forces between a temporary induced dipoles in the neighbouring molecules
what is a permanent dipole-dipole interaction
the weak attractive force between permanent dipoles in neighbouring polar molecules
what is a hydrogen bond?
a strong dipole-dipole attraction between an electron deficit Hydrogen atom on one molecule and a lone pair off electrons and highly electronegative atom (NOF) on a different molecule
How do intermolecular forces occur?
they occur due to the constant random movements of electrons within the shells of atoms in molecules
What is the relative bond strength of.. a ionic and covalent b hydrogen bonding c permanent dipole -dipole forces d London forces
a - 1000
b - 50
c - 10
d -1
How does permanent dipole-induced dipole interaction work
some molecules have a permeant dipole due to polar forces, the polar molecule nears a non-polar molecules and is able to cause the electrons in the shells nearby to shift slightly by being repelled therefore causing the non-polar molecule to become slightly charged and polar therefore the permanent induced dipole has induced a dipole in the other molecule and causes an attraction
How does permanent-dipole permanent dipole interaction happen
moelcules with permanent dipoles will also be attracted to other molecules with permanent dipoles by to the opposite charged end
What are London forces caused by
when non-polar molecules are attracted to one another
this is caused by the constant random movement of electrons in atomic shells this movement unbalanced the distribution of charge within the electron shell, at any moment there will be an instantaneous dipole across the molecule this induces a dipole in the neighbouring molecules
small induced dipoles attract each other
What effect does London forces have on boiling points
as the number of electrons increase so does the strength of the London forces therefore the boiling point increases and more energy is required to break them apart
what effect does hydrogen bonding have on a compound
only effects physical properties
why can ice float
ice is less dense than water
the water molecules to a regular arrangement and hydrogen bonds form therefore the ice has an open lattice, when the ice melts the hydrogen bonds collapse and become more dense as molecules come closer
why do hydrogen bonds have high boiling points
hydrogen bonding is stronger than intermolecular forces therefore the effect of forces has to overcome in order to boil is larger
what are the other properties of water
extra intermolecular forces from hydrogen bonds also explain the high surface tension and viscosity of water b
