Chapter 7 - periodicity

Question 1

Periodicity

Answer 1

➜ a repeating trend in properties across each period

➜ e.g across a period each successive element gains 1 more electron

Question 2

Atomic radius

Answer 2

➜ greater the atomic radius the smaller the attraction

Question 3

Nuclear charge

Answer 3

➜ greater the nuclear charge (number of protons) the greater the attraction

Question 4

Electron shielding

Answer 4

➜ greater the number of shells the greater the shielding and the smaller the attraction

Question 5

Reactivity of Period 2

Answer 5

• reactivity increases down group
• as atomic radius increases down group
• nuclear attraction & ionisation energy decreases down group
• electron shielding increases

Question 6

Ionisation graphs

Answer 6

➜ electron number = work out element
➜ amount of turning points = work out the period
➜ amount of electrons before first turning point = work out the group

Question 7

How to tell which element has higher ionisation energy

Answer 7

➜ a paired electron pair in orbital repel each other = electron is lost easier = this is not the high ionisation energy
➜ p sub shells after further from nucleus than S so whatever has S as the last sub shell has higher ionisation energy

Question 8

First ionisation energy decreases down group

Answer 8

➜ atomic radius increases = electrons being added
➜ more electron shielding = less attraction between nucleus and outer electron
➜ number of proton increase BUT effects of atomic radius and shielding outweigh increased nuclear charge

Question 9

First ionisation energy shows a general increase across period 1 and 2

Answer 9

➜ nuclear charge increases = increase nuclear attraction pulling in shells closer causing
➜ atomic radius to decrease
➜ electrons added to same shell
➜ similar shielding

Question 10

metallic bonding

Answer 10

➜ the strong electrostatic attraction between cations and delocalised electrons
➜ delocalised electrons spread out and move through structure
➜ cations = fixed in position
➜ delocalised electrons = mobile

Question 11

Properties of metals

Answer 11

➜ strong metallic bond
➜ high electrical conductivity (electrons carry charge through structure)
➜ high melting and boiling points (energy required to overcome strong electrostatic forces of attraction)
➜ do not dissolve

Question 12

Giant covalent structures

Answer 12

➜ high melting boiling points = covalent bonds strong = hard to break
➜ insoluble = covalent bonds too strong
➜ non conductors

Question 13

Graphene

Answer 13

➜ single layer of graphite

➜ electrical conductor

Question 14

Graphite

Answer 14

➜ layers are bonded by london forces

➜ 3 out of 4 outer shell electrons used for covalent boding = sea of delocalised electrons so can conduct electricity

Question 15

Melting point trends

Answer 15

➜ melting point increases from group 1 to 14
➜ sharp decrease between 14 and 15
➜ low from 15 to 18

Question 16

Halogens reactivity

Answer 16

• less reactive as u go down
• atomic radius decreases going down
• shielding increases going down
• less nuclear attraction as u go down