2.2.2 Bonding And Structure

Question 1

Ionic bonding

Answer 1

Electrostatic force of attraction between oppositively charged ions formed by electron transfer

Question 2

When are ionic bonds stronger

Answer 2

When ions are smaller

When ions have higher charges

Question 3

Structure of ionic bonds

Answer 3

Arranged in a regular 3d giant ionic lattice

Oppositively charged ions in a regular arrangement

Question 4

Physical properties of ionic compounds

Answer 4

High melting points: strong electrostatic forces of attraction between oppositively charged ions in the lattice
Doesn’t conduct electricity when solid: ions are held together tightly in lattice and can’t move so no charge is conducted
Conducts when molten/in solution: ions are free to move to conduct electricity
Usually soluble in aqueous solvents

Question 5

Covalent bonding definition

Answer 5

Strong electrostatic attractikn between a shared pair of electrons and the nuclei of thr bonded atoms

Question 6

Dative covalent bond

Answer 6

When shared pair of electrons in the covalent bond come from only one of the bonding atoms
Direction of arrow shows direction of donation

Question 7

Average bond enthalpy

Answer 7

Measurement of covalent bond strength

Larger the value the stronger the bond

Question 8

Simple molecular

Answer 8

Intermolecular forces (induced dipole dipole, permanent dipole dipole, hydrogen bonds)

Question 9

Examples of ionic bonding

Answer 9

Sodium chloride

Magnesium oxide

Question 10

Covalent bonding

Answer 10

Iodine
Ice
Carbon dioxide 
Water
Methane

Question 11

Melting and boiling points of giant ionic

Answer 11

High

Giant lattice of ions with strong electrostatic forces between oppositely charged ions

Question 12

Melting and boiling points of simple molecular

Answer 12

Low

Weak intermolecular forces between molecules

Question 13

Ionic solubility in water

Answer 13

Generally good

Question 14

Simple molecular solubility in water

Answer 14

Generally poor

Question 15

Conductivity when solid ionic

Answer 15

Poor

Ions fixed in lattice so cant move

Question 16

Conductivity when solid simple molecular

Answer 16

Poor

No ions to conduct and electrons are localised

Question 17

Conductivity when molten ionic

Answer 17

Good

Ions can move

Question 18

Conductivity when molten simple molecular

Answer 18

Poor

No ions

Question 19

Linear molecule

Answer 19

2 bonding pairs
No lone pairs
Angle 180
Co2

Question 20

Trigonal planar

Answer 20

3 bonding pairs
No lone pairs
Bond angle 120
BF3

Question 21

Tetrahedral

Answer 21

4 bonding pairs
No lone pairs
Bond angle 109.5
SiCl4

Question 22

Pyramidal

Answer 22

3 bonding pairs
1 lone pair
Bond angle 107
NCl3

Question 23

Non-linear

Answer 23

2 bonding pairs
2 lone pairs
Bond angle 104.5
OCl2

Question 24

Octrahedral

Answer 24

6 bonding pairs
No lone pairs
90 degrees
SF6

Question 25

How to explain shape of molecules

Answer 25

State number of bonding pairs and lone pairs State that electrons pairs repel and try to get to a position of maximum repulsion No lone pairs then electron pairs repel equally, lone pairs repel more than bonding pairs State shape and bond angles

Question 26

How do lone pairs effect bond angles

Answer 26

Reduce them | By around 2.5 degrees

Question 27

electronegativity

Answer 27

the relative tendency of an atom in a covalent bond in a molecule to attract electrons in a covalent bond to itself

Question 28

most electronegative atoms

Answer 28

F O N Cl

Question 29

electronegativity across a period

Answer 29

``` increases number of protons increase atomic radius decreases shielding stays the same but electrons are more attracted to the nucleus ```

Question 30

electronegativity down a group

Answer 30

decreases distance between nucleus and outer electrons increases shielding of inner shell electrons increases

Question 31

compounds with similar electronegativity are usually what

Answer 31

covalent | as there is a small electronegativity difference

Question 32

formation of a permanent dipole

Answer 32

also known as a polar covalent bond forms when the elements in the bond have different electronegativities unequal distribution of electrons in the bond and produces a charge separation with delta plus and delta minus ends

Question 33

element with the larger electronegativity takes which symbol

Answer 33

delta minus

Question 34

what is a symmetrical molecule

Answer 34

all bonds identical and no lone pairs

Question 35

symmetrical molecules

Answer 35

will not be polar even if individual bonds within the molecule are polar the dipoles will cancel out due to the symmetrical shape, there is no net dipole movement so the molecule is non-polar

Question 36

compound containing large differences in electronegativity will be what

Answer 36

ionic

Question 37

where do induced dipole-dipole interactions occur

Answer 37

between all molecular substances in noble gases never in ionic

Question 38

another name for induced dipole-dipole forces

Answer 38

London forces

Question 39

induced dipole-dipole forces formation

Answer 39

electrons are constantly and randomly moving electron density fluctuates and parts of the molecule become more or less negative this forms temporary dipoles, which induces dipoles to form in neighbouring molecules induced dipole is always the opposite sign to the original one uses delta plus and minus

Question 40

main factor affecting the size of london forces

Answer 40

more electrons higher the chance of london forces forming makes induced dipole-dipole forces greater so the boiling points are greater

Question 41

explanation for the increased boiling points down the halogens

Answer 41

increased number of electrons in bigger molecules causes increased size of london forces this is why I2 is a solid and Cl2 is a gas

Question 42

explanation for the increased boiling points of the alkane homologous series

Answer 42

increasing number of electrons in the bigger molecules | increased size of the London forces between molecules

Question 43

how can the shape of the molecule affect the size of london forces

Answer 43

long chain alkanes have a larger surface area of contact between molecules for london forces to form whereas branched alkanes have less area of contact so less london forces

Question 44

what affects the size of london forces

Answer 44

amount of electrons | surface area of contact between molecules

Question 45

where do permanent dipole-dipole forces occur

Answer 45

between polar molecules

Question 46

permanent dipole-dipole molecules

Answer 46

occur between polar molecules stronger than london forces so compounds have higher boiling points polar molecules aren't symmetrical, have a permanent dipole and have a bond where there is a significant electronegativity difference between the atoms

Question 47

when does hydrogen bonding occur

Answer 47

in compounds that have a hydrogen atom attached to an electronegative atom (N,O,F) must be a lone pair of electrons available large electronegativity difference between the two atoms

Question 48

what must you show on hydrogen bonding

Answer 48

the lone pair the delta plus and minus bond angle is 180 on a hydrogen bond must label the hydrogen bond

Question 49

which is the strongest type of intermolecular bonding

Answer 49

hydrogen bonding then permanent dipole-dipole induced dipole-dipole

Question 50

why does water have a high boiling point

Answer 50

hydrogen bonding between the molecules

Question 51

examples of molecules that can form hydrogen bonds

Answer 51

alcohols carboxylic acids proteins amides

Question 52

what are the 2 anomalous properties of water

Answer 52

solid form ice can float on liquid form water | high melting/ boiling point

Question 53

how can solid from ice float on liquid form water

Answer 53

as the hydrogen bonds means water can form an open lattice | molecules are held further apart and therefore ice has a lower density