Non-Polar and Polar Molecules

Question 1

what is a dipole

Answer 1

• a type of separation of charge
• when electrons in a bond drift towards the more electronegative element
• resulting in a separation of charge between the atoms

Question 2

what does the overall dipole of a molecule depend on

Answer 2

its shape

Question 3

how do the angles between the bonds relative to each other affect their dipoles

Answer 3

• the individual dipoles and either reinforce each other

- or cancel out each other

Question 4

what therefore makes molecule non-polar

Answer 4

• when the cancellation of the dipoles is complete

- and the molecule has no overall dipole

Question 5

what do you call a molecule in which the dipoles reinforce each other, giving it an overall dipole

Answer 5

polar

Question 6

what group in the periodic table contain diatomic molecules that are non-polar

Answer 6

group 7 (halogens)

Question 7

why are the diatomic molecules from group 7 non-polar

Answer 7

• because the two atoms in each molecule have the same electronegativity (as theyre the same)
• this means that the distribution of electron density of the bonding electrons in either molecule is totally symmetrical
• causing the bonds to be non-polar

Question 8

what is the bond between hydrogen and chlorine like and why

Answer 8

• the bond between them is polar
• because chlorine has a higher electronegativity than hydrogen
• meaning the chlorine atom would be slightly negatively charged and the hydrogen would be slightly positively charged

Question 9

why can the molecule be considered to be polar itself

Answer 9

because the only bond it has is polar (all the bonds are polar)

Question 10

what symbol is used to represent a dipole and how would it be applied to hydrogen chloride

Answer 10

• the symbol is an arrow but with the arrow head being half way through the line
• with a small vertical line through the arrow
• it would be pointing in the direction that the shared electron is travelling
• so from the hydrogen to the chlorine atom

Question 11

what are the bonds between the carbon atom and oxygen atoms in CO2 like

Answer 11

• the carbon atom has double bond with each oxygen atom (C=O)
• the oxygen is more electronegative than the carbon atom
• so the C has a o+ and the Os have a o-

Question 12

what does this mean about the polarity of the bonds and the molecule as a whole and why

Answer 12

• the bonds themselves in the molecule are polar
• but the molecule as a whole is non-polar
• this is because, using the dipole arrows, they would be pointing away from the C and to the O
• this means that the two arrows would be pointing in opposite directions due to the O=C=O structure
• leading to their polarities cancelling out and leaving you with a non-polar molecule

Question 13

what kind of molecule other than non-polar is carbon dioxide called due to its structure

Answer 13

a linear molecule

Question 14

what kind of molecule is boron chloride, BCl3, called due to its structure

Answer 14

a trigonal planar molecule

Question 15

is boron chloride polar or non-polar and why

Answer 15

• non-polar
• although chlorine is more electronegative than the boron atom meaning the B-Cl bond is polar
• the molecules is symmetrical so the dipoles cancel each other out

Question 16

what is tetrachloromethane, CCl4, an example of

Answer 16

a tetrahedral molecule

Question 17

is CCl4 a polar or non-polar molecule and why

Answer 17

• non-polar
• same reasons as the trigonal planar molecule
• all the C-Cl bonds are polar but the dipoles cancel each other out due to the symmetry

Question 18

is CHCl3 polar or non-polar and why

Answer 18

• all the bonds are polar
• but although the molecule is symmetrical, the dipoles reinforce each other
• as the dipole symbol points from the hydrogen to the carbon while the others point from the carbon to the chlorine
• resulting in an overall dipole ‘downwards; if hydrogen were to be at the top, making it polar

Question 19

what kind of molecule is water due to its structure

Answer 19

a v shaped molecule

Question 20

is a water molecule polar or non-polar

Answer 20

• polar
• the O-H bonds are polar as the oxygen is more electronegative, meaning both arrows point from the hydrogen to the oxygen
• this means that the dipoles reinforce each other so there is an overall dipole ‘upwards’ assuming the oxygen atom is at the top