Module 2: Intermolecular Forces and Electronegativity Flashcards
What are intermolecular forces?
Attraction between one molecule and a neighbouring molecule of the same substance
What are dipole-dipole attractions?
An attraction between polar molecules with a permanent dipole (attraction between oppositely charged molecules, net attractive force)
What is hydrogen bonding?
A form of dipole-dipole attraction where a hydrogen is attracted to an oxygen, nitrogen or fluorine atom and a pair of love electrons
How strong are hydrogen bonds?
1/10th the strength of covalent bonds
What are London forces?
Temporary dipole attraction in all molecules
Why would a molecule only have London forces?
Because it is symmetrical and cannot hydrogen bond
How do London forces change?
As the size of the molecule increases, the more electrons it has also increased which increases the overall induced dipole attractions
Why do branched alkanes have lower boiling points?
Less surface contact due to non flat shape, therefore less interaction of London forces
What is electronegativity?
Ability of an atom in a covalent bond to attract a bonded pair of electrons towards itself
How does electronegativity changed down a group?
Decreases
How does electronegativity change across a period?
Increases
What is the most electronegative element?
Fluorine
What is a pure covalent bond?
A bond between two atoms with the same electronegativity so the shared pair of electrons equally, e.g. H2
What happens when atom A is more electronegative than atom B?
Atom A becomes slightly negative, atom B becomes slightly positive
What is the name for an uneven distribution of a covalent bond?
Polar
