Ionic Bonding

Question 1

what does ionic bonding consist of

Answer 1

• a regularly arranged array of oppositely charged ions

- extending throughout a giant lattice network

Question 2

what does ionic bonding usually make

Answer 2

solid materials (and salts)

Question 3

even though ionic compounds have ions of the same charge close to each other, why does their structure still remain

Answer 3

because the ions are arranged in such a way that the electrostatic attractions between the oppositely charged ions are greater then the repulsion between ions of the same charge

Question 4

how do you determine the strength of ionic bonds

Answer 4

• by calculating the amount of energy needed
• in one mole of the solid
• to separate the ions to infinity

Question 5

why ‘infinity’

Answer 5

because when they are that distance apart they can no longer interact

Question 6

what are the units for this calculation

Answer 6

kJ mol-1

Question 7

what are the two main factors that affect the amount of energy needed

Answer 7

• size of the ions

- charge of the ions

Question 8

what is the relationship between the amount of energy required to separate the ions to infinity and the their size

Answer 8

a decrease in size results in more energy being required

Question 9

what is the relationship between the amount of energy required to separate the ions to infinity and the their charge

Answer 9

an increase in the charge of both ions results in more energy being required

Question 10

what is the trend in ionic radii as you go down group 1

Answer 10

as you go down group 1 their atomic radii increases

Question 11

what is the trend in ionic radii as you go down group 7

Answer 11

as you go down group 7 their atomic radii increases

Question 12

why do they increase in both cases

Answer 12

• because the number of electron shells they have increases

- so the ions would naturally get larger

Question 13

what is the trend in ionic radii as you go across period 2 and 3

Answer 13

• they decrease

Question 14

why does the ionic radii across periods decrease

Answer 14

• because across the period the number of electron shells isnt changing
• but the nuclear charge is increasing
• resulting in stronger electrostatic forces of attraction pulling the electrons towards the nucleus
• leading to a smaller ionic radius

Question 15

why are the boiling points of ionic solids so high

Answer 15

• they consist of a giant lattice network of oppositely charged ions
• with so many ions being present, the combined electrostatic forces of attraction amongst them is very strong
• resulting in a large amount of energy being required to overcome them

Question 16

why are ionic solids in the form of crystals brittle when stress is placed on them

Answer 16

• the layers of ions slide over each other due to the stress
• this causes ions of the same charge to be side by side and therefore repel each other
• making it easy for the crystal to break apart

Question 17

why cant solid ionic compounds conduct electricity

Answer 17

• because there are no delocalised electrons

- the ions are also not free to move under the influence of a potential difference

Question 18

when would an ionic compound only be able to conduct electricity and why

Answer 18

• when its in a molten or aqueous state
• because the ions would be fluid and free to move
• therefore being able to carry a current through them

Question 19

why are ionic solids soluble despite their bonds being so strong

Answer 19

• the energy required to break the lattice structure and separate the ions
• can be supplied by the hydration of the separated ions produced
• this means that both positive and negative ions from the ionic solid are attracted to water molecules due to its polarity

Question 20

how does the polarity and structure of water cause positive and negative ions to be attracted to it

Answer 20

• the oxygen atom in the water molecule has a partial negative charge
• so the oxygen end of the molecule would be attracted to positive ions
• the hydrogen atoms in the water molecule have partial positive charges
• so the hydrogen end of the molecule would be attracted to negative ions

Question 21

what are cations and anions

Answer 21

• cation = positive ion

- anion = negative ions

Question 22

when are cations and anions produced

Answer 22

• when an ionic compound is formed

- from the reaction between a metal and non-metal

Question 23

what would be the dot and cross diagram of the reaction 2Na + Cl2 = 2NaCl

Answer 23

• you would draw the two Na atoms with one electron on their outer shell (crosses)
• the chlorine molecule consisting of two chlorine atoms with their outer electrons (dots)
• then show what they become after the reaction
• being [Na]+ [Cl(7 dots 1 cross)]- [Na]+ [Cl(7 dots 1 cross)]-
• twice because of the 2NaCl

Question 24

what is the biggest evidence for the existence of electrons

Answer 24

electrolysis

Question 25

how is electrolysis set up

Answer 25

you have a positive and negative electrode formed by a d.c. current placed into a molten / aqueous state of an ionic compound

Question 26

if the ionic compound were to be sodium chloride, how would this electrolysis prove that ions are at play

Answer 26

• when a direct current is passed through the ionic compound, the positively charged sodium ions migrate to the cathode
• while the negatively charged chlorine ions migrate to the anode
• the sodium ions would gain electrons and be discharged as solid sodium
• while the chlorine ions lose electrons and is discharged as chlorine gas

Question 27

what are the half equations for this happening to the sodium and chlorine atoms

Answer 27

• 2Na+ + 2E- = 2Na

- 2Cl- = Cl2 + 2e-