Electronegativity

Question 1

polar covalent bond

Answer 1

a bond with a permanent dipole, having partial positive and partial negative charges on the bonded atoms.

Question 2

polar molecule

Answer 2

a molecule with an overall dipole having taken into account any dipoles across bonds and the shape of the molecule

Question 3

non-polar

Answer 3

with no charge separation across a bond or within a molecule (when theres symmetrical distribution of electron density)

Question 4

pauling electronegativity value

Answer 4

a value assigned as a measure for relative attraction of a bonded atom for the shared pair of electrons in a covalent bond

Question 5

electronegativity

Answer 5

the ABILITY of an atom to attract the bonding electrons in a covalent bond

Question 6

how to answer electronegativity questions

Answer 6

Chlorine is more electronegative than Hydrogen
It has a greater attraction for the bonded pair of electrons than H, so it is a polar covalent bond.
It is polarised with a partial positive on H and partial negative on Cl

Question 7

dipole

Answer 7

a separation in electrical charge so that one atom of a polar covalent bond/ one end of a polar molecule has a partial positive/negative charge

Question 8

permanent dipole

Answer 8

a small charge difference that doesn’t change across a bond, with partial positive and negative on the bonded atoms, the result of them having different electronegativities

Question 9

intermolecular forces

Answer 9

attractive forces between DIPOLES of molecules (london forces, hydrogen bonds, permanent dipole-dipole interactions)

Question 10

London forces

Answer 10

attractive forces between INDUCED dipoles in different molecules, which are TEMPORARY and relatively weak

Question 11

Increase strength of induced dipole-dipole interactions

Answer 11

• larger particle size and more electrons: greater instantaneous/induced dipoles, greater induced dipole-dipole interactions, stronger attractive forces between molecules, more energy needed to separate particles = higher mp/bp
• more points of contacts/SA of contact i.e. linear than branched = greater induced dipole-dipole interactions

Question 12

covalent bonds determine

Answer 12

chemical reactions and identity of molecule

Question 13

intermolecular forces determine

Answer 13

mp/bp, physical properties

Question 14

permanent dipole dipole interactions

Answer 14

attractive forces between the permanent dipoles in different molecules

Question 15

simple molecular lattice

Answer 15

a three dimensional structure of molecules bonded together by weak inter molecular forces

Question 16

molecule

Answer 16

the smallest part of a COVALENT COMPOUND that can exist whilst retaining its chemical identity, consisted of two or more atoms covalently bonded together

Question 17

when changing state, what breaks?

Answer 17

intermolecular forces, not the covalent bonds

Question 18

hydrogen bonding

Answer 18

the dipole dipole interaction between an electron deficient hydrogen attached to an electronegative atom on one molecule and a lone pair of electrons on the electronegative nitrogen, fluorine or oxygen on another molecule. (must be polar covalent with permanent dipoles therefore)

Question 19

for hydrogen bonding

Answer 19

• must be small atoms (high charge density- partial charge is concentrated)
• must have lone pair
• must be electronegative

Question 20

ice structure shape

Answer 20

hydrogen bonds hold molecules apart in an:
open tetrahedral shape lattice full of holes
open lattice
= less dense, inc volume

Question 21

when ice lattice breaks vs when water boils

Answer 21

rigid arrangement of hydrogen bonds break vs hydrogen bonds break completely

Question 22

water anomalous properties

Answer 22

high bp/mp (-75C bp without), ice less dense than water, high surface tension and high viscosity

Question 23

why is it hard to predict polar simple molecules solubility

Answer 23

it depends on the strength of the dipole