Physical- Molecules

Question 1

Shapes of simple molecules when it has 2 pairs of electrons:

Answer 1

• Shape = linear molecule
• Bond angles = 180
• Example = BeCl2

Question 2

What do the two bonding pairs of electrons do in a linear molecule?

Answer 2

They both repel each other- the position of maximum repulsion for the pairs of bonding electrons is 180 degrees

Question 3

Shapes of simple molecules when it has 3 pairs of electrons:

Answer 3

• Shape = trigonal planar molecule
• Bond angles = 120
• Example = BCl3

Question 4

Shapes of simple molecules when it has 4 pairs of electrons:

Answer 4

• Shape= tetrahedral molecule
• Bond angles = 109.5
• Example = CH4

Question 5

Shapes of simple molecules when it has 5 pairs of electrons:

Answer 5

• Shape = trigonal bipyramidal molecule
• Bond angles = 120, 90
• Example = PF5

Question 6

Shapes of simple molecules when it has 6 pairs of electrons:

Answer 6

• Shape = octahedral molecule
• Bond angles = 90
• Example = SF6

Question 7

Shapes of molecules when there is a lone pair of electrons

Answer 7

The shape of the molecule will become distorted as the lone pair of electrons produce more repulsion. The l.p.e has an electron cloud that is more concentrated than a bonding pair.

Question 8

What is the order of repulsion for molecules?

Answer 8

lone pair - lone pair
lone pair - bond pair
bond pair - bond pair

Question 9

What happens to a tetrahedral molecule when there is a l.p.e?

Answer 9

Any tetrahedral with one l.p.e becomes a trigonal pyramidal, the bond angle also changes to 107 degrees as the l.p.e exerts a greater of repulsion than the bonding pairs

Question 10

Define the term electronegativity

Answer 10

The power of an atom to attract the two electrons in a covalent bond

Question 11

What is the trend in electronegativity as you go down a group?

Answer 11

Decreases:
- the atom gets bigger
- more shielding
- weaker attraction between protons and nucleus

Question 12

What is the trend in electronegativity as you go across a period?

Answer 12

Increases:
- the atom gets smaller
- less shielding
- more protons
- stronger attraction between protons and nucleus

Question 13

What is a polar bond?

Answer 13

A covalent bond where the two electrons are not shared equally

Question 14

What is a non-polar bond?

Answer 14

A covalent bond where the two electrons are shared equally

Question 15

When does a polar bond happen?

Answer 15

When the two atoms in a covalent bond have a different electronegativity

Question 16

When does a non-polar bond happen?

Answer 16

When the two atoms in a covalent bond have the same electronegativity

Question 17

What are intramolecular forces?

Answer 17

Forces that occur WITHIN a molecule and are usually covalent bonds

Question 18

What are intermolecular forces?

Answer 18

Forces that are BETWEEN the molecules

Question 19

What are the three types of intermolecular forces?

Answer 19

Van der Waals forces
Permanent Dipole attractions
Hydrogen bonds

Question 20

What is the order of strengths of intermolecular forces?

Answer 20

-hydrogen bonds (strongest)
-permanent dipole-dipole
- van der Waals forces (weakest)

Question 21

Why do Van der Waals forces occur?

Answer 21

Because the electrons are constantly moving around so there will be an uneven electron distribution