1.03 Bonding

Question 1

What is ionic bonding ?

Answer 1

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

Question 2

Give an example of an ionically bonded substance.

Answer 2

NaCl.

Question 3

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

Answer 3

High - it 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.

Question 5

What is simple molecular covalent bonding ?

Answer 5

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

Question 6

Are there any lone electrons in simple covalent bonding ?

Answer 6

No - they are all involved in bonding.

Question 7

Can simple molecular covalent molecules conduct electricity ? Why ?

Answer 7

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

Question 8

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

Answer 8

Low - weak van der Waals forces of attraction between molecules that don’t take much energy to overcome.

Question 9

Describe macromolecular covalent bonding.

Answer 9

Lattice of many atoms held together by strong covalent bonds.

Question 10

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

Answer 10

High, as it takes a lot of energy to overcome many strong covalent bonds.

Question 11

Do substances with macromolecular bonding conduct electricity ?

Answer 11

Most don’t as typically all electrons are used in bonding.

Question 12

Draw / describe the 3D structure of diamond.

Answer 12

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

Question 13

Draw / describe the structure of graphite.

Answer 13

A macromolecular covalent molecule
Each C atom is only bonded to 3 others
It comes in layers, weak van der Waals between layers mean they can slide over each other (soft / slippery)
One electron from each carbon is delocalised and can carry charge (conducts electricity)

Question 14

Describe and draw metallic bonding.

Answer 14

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

Question 15

Do metallic compounds have a high/low mpt and bpts? Why ?

Answer 15

High, as strong forces of attraction between positive metal ions and negatively charged sea of electrons.

Question 16

Do metallic compounds conduct electricity ? Why?

Answer 16

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

Question 17

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

Answer 17

Increases as you go right, giving a higher mpt and bpt for those metals
The higher charge of metal ions results in more delocalised electrons per ion
This gives a stronger force of attraction in turn.

Question 18

Define electronegativity.

Answer 18

The ability of an atom to attract a pair of electron in a covalent bond.

Question 19

What affects electronegativity ?

Answer 19

Nuclear charge
Atomic radius/electron shielding

Question 20

What is the most electronegative element ?

Answer 20

Fluorine (4.0)
This is because it has the largest nuclear charge for its electron shielding and a small atomic radius.

Question 21

How do you get a nonpolar bond ?

Answer 21

Both bonding elements have similar electronegativities.

Question 22

When do you get a polar bond ?

Answer 22

Bonding atoms have different enough electronegativities.

Question 23

What is the strongest type of intermolecular force ?

Answer 23

Hydrogen bonding.

Question 24

What is the weakest type of intermolecular force ?

Answer 24

Van der waals forces.

Question 25

Describe van der waals forces.

Answer 25

•Temporary dipoles are created by the random movement or electrons
•This induces a dipole in a neighbouring molecule
•This causes a temporary induced dipole-dipole attraction aka van der waals forces.

Question 26

Are van der waals forces stronger in smaller or larger molecules ?

Answer 26

In larger molecules as there are more electrons to create temporary dipoles.

Question 27

Describe permanent dipole-dipole attraction

Answer 27

•Some molecules with polar bonds have permanent dipoles
•This induces a force of attraction between those dipoles and those of neighbouring molecules.

Question 28

What conditions are needed for hydrogen bonding to occur ?

Answer 28

•O-H, N-H, F-H
•These molecules (O, N, F) all have lone pairs and are very electronegative
•This causes a strong force of attraction between H nucleus and the lone pair on the other atoms.

Question 29

Why is ice less dense than water ?

Answer 29

In liquid water hydrogen bonds are constantly breaking and reforming as molecules freely move
In ice the hydrogen bonds hold the molecules in fixed positions; holding them slightly further apart than that of liquid water.

Question 30

What is a dative/co-ordinate bond ? When are they formed ?

Answer 30

They are formed when an electron deficient atom/ion accepts a lone pair of electrons from another atom/ion (this atom is not used in bonding)

Question 31

What does the shape of molecules depend on ?

Answer 31

•The number of electrons in the valence shell of the central atom
•The number of these electrons which are in bonds or lone pairs

Question 32

What does electron pair repulsion theory state ?

Answer 32

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

Question 33

Which pairs experience the most repulsion ?
Lone pair-Lone pair
Lone pair-Bonded pair
Bonded pair-Bonded pair

Answer 33

LP-LP - most
LP-BP - middle
BP-BP - least.