Shapes of Molecules

Question 1

What is electron pair repulsion theory?

Answer 1

each pair of electrons around an atom will repel all other electron pairs the pairs of electrons will therefore take up positions as far apart as possible to minimise repulsion

Question 2

What are the properties of molecules with 2 shared pairs of electrons?

Answer 2

180 called linear e.g. CO2

Question 3

What are the properties of molecules with 3 shared pairs of electrons?

Answer 3

120 trigonal planar e.g. boron trifluoride

Question 4

What are the properties of molecules with 4 shared pairs of electrons?

Answer 4

109.5 tetrahedral e.g. methane and ammonium

Question 5

What are the properties of molecules with 5 shared pairs of electrons?

Answer 5

120 and 90 trigonal bipyramid e.g. phosphorus pentachloride

Question 6

What are the properties of molecules with 6 shared pairs of electrons?

Answer 6

90 octahedral

Question 7

Name this:

Answer 7

trigonal planar

Question 8

Name this:

Answer 8

tetrahedral

Question 9

Name this:

Answer 9

trigonal bipyramidal

Question 10

Name this:

Answer 10

octahedral

Question 11

explain why CF4 has a bond angle of 109.5

Answer 11

• AROUND carbon there are 4 bonding pairs of electrons and no lone pairs
• therefore, these repel equally and spread as far as possible

Question 12

Account for the shape of the BF – 4 ion and state the bond angle present

Answer 12

• Equal repulsion between bonding pairs/bonds/bonding electrons 1 09(½)