Bonding and Structure 3

Question 1

Why do giant covalent structures have high melting and boiling point?

Answer 1

Strong covalent bonds within the molecules need to be broken which requires a lot of energy

Question 2

Draw and describe the structure of a diamond

Answer 2

3D tetrahedral structure of C atoms, with each C atom

bonded to four others

Question 3

What does the shape of a molecule depend on?

Answer 3

Number of electron pairs in the outer shell

Number of these electrons which are bonded and
lone pairs

Question 4

What is the shape, diagram

and bond angle for BeCl2

Answer 4

Linear
180
o-o-o

Question 5

What is the shape, diagram

and bond angle for BCl3?

Answer 5

Trigonal planar
120°

     o
      |
     o
   /    \
o        o

Question 6

What is the shape, diagram and
bond angle for CH4
?

Answer 6

Tetrahedral
109.5

   o
    |
   o ------o
 /    \\
o      o

Question 7

What is the shape,diagram
and bond angle for PCl5
?

Answer 7

Trigonal bipyramid
90° and 120°

      o
       |
o\_\_o-------o
       |   \\
      o     o

Question 8

What is the shape, diagram
and bond angle for SF6
?

Answer 8

Octahedral
90°

          o
o --     |     -- o
       -- o --
       //  | \\
     o    |   o
           o

Question 9

What is the shape, diagram
and bond angle for NH3
?

Answer 9

Pyramidal
107°

        . .
        N 
H  /  |||  =  H
        |||
        H

Question 10

What is the shape, diagram

and bond angle for H2O?

Answer 10

Non linear
104.5°

 O    /    \ H       H

Question 11

What is the shape, diagram

and bond angle for NH4+

Answer 11

Tetrahedral
109.5°

[      H              ] +
[       |               ]
[      N ----        ]
[    /   \\       H   ]
[ H      H          ]

Question 12

By how many degrees does
each lone pair reduce the
bond angle?

Answer 12

2.5°

Question 13

Define electronegativity

Answer 13

The ability of an atom to attract the pair
of electrons (the electron density) in a
covalent bond

Question 14

What scale is
electronegativity measured
on?

Answer 14

Pauling scale

Question 15

In which direction of the
periodic table does
electronegativity increase?

Answer 15

Top right, towards fluorine

Question 16

What does it mean when the

bond is non-polar?

Answer 16

The electrons in the bond are evenly

distributed

Question 17

What is the most

electronegative element?

Answer 17

Fluorine

Question 18

How is a polar bond formed?

Answer 18

Bonding atoms have different

electronegativities

Question 19

Why is H2O polar, whereas
CO2
is non polar?

Answer 19

CO2
is a symmetrical molecule, so there
is no overall dipole

Question 20

What is meant by

intermolecular force?

Answer 20

Attractive force between neighbouring

molecules

Question 21

What are the 3 types of

intermolecular forces?

Answer 21

● Hydrogen bonding
● Permanent dipoles
● London forces

Question 22

Describe permanent dipole induced dipole interaction

Answer 22

When a molecule with a permanent dipole is
close to other non polar molecules it causes
the non polar molecule to become slightly
polar leading to attraction

Question 23

Describe permanent dipole-permanent dipole interactions

Answer 23

Some molecules with polar bonds have
permanent dipoles → forces of attraction
between those dipoles and those of
neighbouring molecules

Question 24

Describe London forces

Answer 24

● London forces are caused by random movements of
electrons
● This leads to instantaneous dipoles
● Instantaneous dipole induces a dipole in nearby
molecules
● Induced dipoles attract one another

Question 25

Are London forces greater in

smaller or larger molecules?

Answer 25

Larger due to more electrons