1.3 - Bonding

Question 1

What ionic bonding?

Answer 1

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

Question 2

An example of an ionically bonded substance.

Answer 2

NaCl (sodium chloride - salt)

Question 3

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

Answer 3

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

Question 4

Do ionic compounds conduct electricity? Why?

Answer 4

Yes, when molten or in solution as the ions are free to move and carry charge but they don’t when they are solid.

Question 5

What is simple molecular covalent bonding?

Answer 5

Strong covalent bonds between atoms, weak Van Der Waals forces of attraction between the molecules.

Question 6

Are there any lone electrons in simple covalent bonding?

Answer 6

No - all involved in bonding.

Question 7

Can simple molecular covalent molecules conduct electricity? Why?

Answer 7

No - all electrons are used in bonding so there aren’t any free electrons to move around.

Question 8

Do simple molecular substances have a high/low MP and BP? Why?

Answer 8

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 9

Describe the macromolecular covalent binding.

Answer 9

Lattice of many atoms held together by strong covalent bonds.

Question 10

Do substances with macromolecular covalent bonds have high/low MP and BP? Why?

Answer 10

High - it takes a lot of energy to overcome many strong covalent forces.

Question 11

Do substances with macromolecular covalent bonds conduct electricity?

Answer 11

Most of them don’t as all the electrons are used in bonding.

Question 11

Describet the structure of graphite.

Answer 11

• Similar to diamond - maromolecular covalent - but each C atom is only bonded to 3 others, so its in layers.
• Weak Van der Waals forced of attractions between layers which allows it to slide over each other -> soft, slippery.
• One electron from each carbon is delocalised and can carry charge -> conducts electricity.

Question 11

Describe the structure of diamond.

Answer 11

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

Question 11

Define electronegativity.

Answer 11

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

Question 11

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

Answer 11

• It increases due to higher MP and BP.
• Its stronger.
• Higher charge on metal ions.
• More delocalised electrons per ions.
• Stronger forces of attractions between them.

Question 12

What effects electronegativity? (3)

Answer 12

• Nuclear charge
• Atomic radius
• Electron shielding

Question 12

DO metallic compounds conduct electricity? Why?

Answer 12

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

Question 12

Describe metallic bonding.

Answer 12

Lattice of positive metal ions strongly attracted to a sea of delocalised electrons. Layers can slide over each other - malleable (can be formed into different shapes).

Question 12

Do metallic compounds have high/low MP and BP? Why?

Answer 12

Both are high as strong forces of attraction between positive metal ions and negatively charged sea of delocalised electrons.

Question 13

What id the most electronegative element?

Answer 13

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

Question 14

How do you get non-polar bonds?

Answer 14

Both bonding elements have the same electronegativities.

Question 15

When do you get polar bonds?

Answer 15

When the bonding atoms have different electronegativities.

Question 16

What is the strongest type of IMF?

Answer 16

Hydrogen bonding.

Question 17

What is the weakest IMF?

Answer 17

Van der Waals.

Question 18

Describe the Van der Waals forces of attraction.

Answer 18

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

Question 19

Are Van der Waals forces stronger in smaller or larger molecules?

Answer 19

Larger - more electrons.

Question 20

Describe permanent dipole-dipole attraction.

Answer 20

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

Question 21

What conditions are needed for hydrogen bonding to occur?

Answer 21

• O-H, N-H or F-H, lone pair of electrons on O, F, N.
• Becaouse O, N and F are highly electronegative, H nucleus is left exposed.
• Strong force of attraction between H nucleus and lone oair of electrons on O, N, F.

Question 22

Why is ice less dense than liquid water?

Answer 22

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

Question 23

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

Answer 23

Formed when an electron deficient atom/ion/ accepts a lone pair of electrons from an atom/ion with a lone pair of electons.

Question 24

What does the shape of molecules depend on?

Answer 24

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

Question 25

What does teh ‘Electron Pair Repulsion Theory’ state?

Answer 25

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

Question 26

Which experience the most repulsion?
LP-LP
LP-BP
BP-BP

Answer 26

LP-LP: strongest repulsion.
LP-BP: middle repulsion.
BP-BP: Weakest repulsion.