OZ1 (Intermolecular Forces + Electronegativity)

Question 1

describe the trend of electronegativity down a group and across a period

Answer 1

decreases down a group as shielding increases and atomic radius increases so charge density is reduced
increases along a period as the atomic radius decreases and charge density increases

Question 2

how is a permanent dipole formed

Answer 2

if there are two significantly different electronegativities a polar bond forms and the more electronegative atom draws more of the negative charge towards itself

Question 3

what are polar molecules

Answer 3

where there is a difference in polarity across the molecule and the bonds do not cancel out, they can align with others to form a lattice of molecules

Question 4

what are induced dipoles

Answer 4

when the electron arrangement is influenced by the distributions of electrons on another particle

Question 5

what does the strength of induced dipoles depend on

Answer 5

the larger the Mr, the stronger the forces
as chain length increases, mr increases so ID does causing a higher BP
branching means they’re less able to pack tightly together so the distance they cover increases and the forces are weakened so they have a lower BP

Question 6

how do IM forces vary down group 7

Answer 6

the Mr increases down the group so IM does too which means it takes more energy to break them

Question 7

what is hydrogen bonding between

Answer 7

the hydrogen atom and nitrogen, oxygen or fluorine
the lone pair of electrons on these en atoms forms a bond with the polar postier H atom

Question 8

why does ice have a lower density than water

Answer 8

the hydrogen bonds hold the molecules in a rigid structure with a lot of air gaps

Question 9

what do hydrogen bonds cause in alcohols

Answer 9

a higher boiling point than alkanes with similar Mr, the lone pair of electrons on the O forms hydrogen bonds with the H on the -OH