Unit 1: Section 3 - Bonding

Question 1

What is ionic bonding?

Answer 1

Strong electrostatic forces of attraction between oppositely charged ions held in a lattice

Question 2

How high are ionically bonded substances’ bp and mp? Why?

Answer 2

High - takes alot of energy to break strong electrostatic forces of attraction between oppositely charged ions

Question 3

Do ionic compounds conduct electricity? Why?

Answer 3

Yes - when molten/ in solution as the ions are free to move and carry charge (doesn’t when solid)

Question 4

What is simple molecular covalent bonding?

Answer 4

Strong covalent bonds between atoms, weak van der Waals forces of attraction between molecules

Question 5

Are there any lone electrons in simple covalent bonding?

Answer 5

No - all involved in bonding

Question 6

Can simple molecular covalent molecules conduct electricity? Why?

Answer 6

No - all electrons are used in bonding and aren’t free to move

Question 7

Do simple molecular substances have a high/low mpt and bpt? Why?

Answer 7

Low - weak van der Waals forces of attraction between molecules that don’t take much energy to overcome (these are overcome rather than covalent bonds)

Question 8

Describe macromolecular covalent bonding

Answer 8

Lattice of many atoms held together by strong covalent bonds

Question 9

Do substances with macromolecular covalent bonds have high/low mpt and bpts? Why?

Answer 9

High - it takes alot of energy to overcome many strong covalent bonds

Question 10

Do substances with macromolecular covalent bonds conduct electricity?

Answer 10

Most don’t as all electrons are used in bonding

Question 11

Describe the structure of diamond

Answer 11

3D tetrahedral structure of C atoms, with each C atom bonded to 4 others

Question 12

Describe the structure of graphite

Answer 12

• Similar to diamond - macromolecular covalent - but each C atom is only bonded to 3 others, so it is in layers
• Weak van der Waals forces of attraction between layers mean they can slide over each other - soft, slippery
• One electron from each carbon is delocalised and carry charge - conducts electricity

Question 13

Describe metallic bonding

Answer 13

Lattice of positive metal ions strongly attached to a sea of delocalised electrons
Layers can slide over each other - malleable

Question 14

Do metallic compounds have high/low bpt and mpts? Why?

Answer 14

High - strong forces of attraction between positive metal ions and negatively charged sea of delocalised electrons

Question 15

Do metallic compounds conduct electricity? Why?

Answer 15

Yes as delocalised electrons can move throughout the metal to carry charge

Question 16

How does the strength of metallic bonds change across the periodic table? Why?

Answer 16

Increases
* Higher melting and boiling points
* Higher charge on metal ions
* More delocalised electrons per ion
* Stronger force of attraction between them

Question 17

What is the definition of electronegativity?

Answer 17

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

Question 18

What 3 things affect electronegativity?

Answer 18

• Nuclear charge
• Atomic radius
• Electron shielding

Question 19

What is the most electronegative element?

Answer 19

Fluorine - largest nuclear charge for its electron shielding, small atomic radius

Question 20

How do you get a non polar bond?Q

Answer 20

Both bonding elements have the same electronegativities

Question 21

When do you get a polar bond?

Answer 21

Bonding atoms have different electronegativities

Question 22

What is the strongest type of intermolecular force?

Answer 22

Hydrogen bonding

Question 23

Describe van der Waals’ forces of attraction

Answer 23

Temporary dipoles are created by the random movement of electrons -> induces dipole in neighbouring molecules -> temporary induced dipole-dipole attraction aka van der Waals forces of attraction

Question 23

What is the weakest type of intermolecular force?

Answer 23

van der Waals forces

Question 24

Are van der Waals forces greater in smaller or larger molecules?

Answer 24

Larger - more electrons

Question 25

Describe permanent dipole-dipole attraction

Answer 25

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

Question 26

What conditions are needed for hydrogen bonding to occur?

Answer 26

• O-H, N-H or F-H bond
• Lone pair of electrons on O, F or N
• Because O, N and F are hgihly electronegative, H nucleus is left exposed
• Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

Question 27

Why is ice less dense than liquid water?

Answer 27

• In liquid water, hydorgen bonds constantly break and reform as molecules move about
• In ice, the hydrogen bonds hold the molecules in fixed positions; this makes them slightly further apart than in liquid water

Question 28

What is a dative/co-ordinate covalent bond? When is it formed?

Answer 28

Formed when an electron deficient atom/ion accepts a lone pair of electrons from an atom/ion with a lone pair of electrons (not used in bonding)

Question 29

What does the shape of molecules depend on?

Answer 29

• Number of electrons in the valence shell of the central atom
• Number of these electrons which are in bonded or lone pairs

Question 30

What does the electron pair repulsion theory state?

Answer 30

Electron pairs will take up positions as far away from each other as possible, to minimise the repulsive forces between them

Question 31

Which intermolecular forces experience the most repulsion?

Answer 31

LP-LP repulsion is strongest
LP-BP repulsion is in the middle
BP-BP repulsion is weakest

Question 32

What is the shape and bond angle of 2 bonded pairs and 0 lone pairs?

Answer 32

Linear, 180°

Question 33

What is the shape and bond angle in a shape with 3 bonding pairs and 0 lone paris?

Answer 33

Trigonal planar, 120°

Question 34

What is the shape and bonding with bonded pairs and 0 lone pairs?

Answer 34

Tetrahedral, 109.5°

Question 35

What is the shape and bond angle with 5 bonded pairs and 0 lone pairs?

Answer 35

Trigonal bipyramidal, 90° and 120°

Question 36

What is the shap