Chapter 7 - Periodicity

Question 1

a period is a ?

Answer 1

row across the periodic table. All elements in the same period have the same number of shells

Question 2

A group is ?

Answer 2

the column going down the table. Elements in the same group have their outer electron in the same position e.g. group 1 elements have their outer electron in the 2s orbital

Question 3

periodicity is?

Answer 3

a repeated trend in properties across any period of the periodic table

Question 4

trends in electron configuration across periods 2 & 3?

Answer 4

order in which subshells fill up

s -> p -> d

Question 5

properties across a period?

Answer 5

• across a period, type of structure/ bonding changes
• metallic -> giant covalent -> simple molecular -> monatomic
• electrical conductivity changes - metallic yes, ionic sometimes, covalent, no except graphite

Question 6

melting/ boiling point across a period?

Answer 6

depends on the type of structure/ bonding

- metallic = high, giant covalent = very high, simple molecular = low

Question 7

atomic radius definition?

Answer 7

Atomic radius is related to the distance from the nucleus of an atom to the outer shell electron. The larger the atomic radius, the larger the atom

Question 8

nuclear charge?

Answer 8

the more protons in the nucleus, the more strongly outer electrons are attracted, the smaller the atomic radius

Question 9

shielding?

Answer 9

• the repulsion between electrons in inner shells reduces the attraction the outer electrons feel from the nucleus
• SAME ACROSS PERIOD

Question 10

why does atomic radius decrease across periods?

Answer 10

• bigger nuclear charge pulls outer electrons closer to the nucleus
• shielding stays the same
• the increasing no. of outer electrons are all in the same shell

Question 11

why does atomic radius increase down a group?

Answer 11

• NC increases
• s increases
• number of shells increases so attraction between nucleus & outer shell electrons decreases

Question 12

first Ionisation Energy equation ?

Answer 12

Na (g) - e (^-) -> Na plus (g)

STATE SYMBOLS

Question 13

1st IE definition?

Answer 13

the energy required to remove one electron from each atom in one mole of gaseous atoms to form gaseous 1+ ions

Question 14

why is energy needed for the 1st IE

Answer 14

overcome the attractive force between the nucleus and the electron that is being removed

Question 15

effect of increasing nuclear charge on 1st IE?

Answer 15

• Higher IE = more energy needed to remove the electron as electron more strongly attracted

Question 16

effect of increasing atomic radius on 1st IE?

Answer 16

lower IE

as electron is further away from pull of nucleus

Question 17

effect of increasing shielding on 1st IE?

Answer 17

lower IE

as outer electron feels attraction of nucleus less

Question 18

trends in 1st IE across period 3?

Answer 18

• IE increases
  as NC increases, Shielding stays same, Atomic radius decreases
• outer e are attracted to nucleus more strongly
• more energy needed to remove em

Question 19

irregularities in 1st IE can be explained in terms of ?

Answer 19

electron arrangement

Question 20

Why is less energy needed to remove 1 electron from Al?

Answer 20

the 3p electron is further away from nucleus than the 3s electrons so less strongly attracted, therefore lower energy to remove 3p electron.

Question 21

why is less energy needed to remove 1 electron from S?

Answer 21

removing this electron removes the repulsion between 2 electrons in one p orbital therefore requires less energy
– this always happens when removing 4th electron from p subshell

Question 22

summary of trends across period 3?

Answer 22

• Atomic radius decreases
• 1st IE increases
• MP& BP - increase to a max., decreases sharply

Question 23

if enough energy is applied, all ….

Answer 23

electrons can be removed from an atom

Question 24

definition: 2nd IE?

Answer 24

energy needed to remove 1 electron from each ion in 1 mole of gaseous atoms forming one mole of gaseous 2+ ions

Question 25

why do successive IE increase?

Answer 25

as we remove e-, the proton: electron ratio increases and electrons are attracted more strongly by the nucleus, decreasing the radius of the ION.

Question 26

successive IE: new shell?

Answer 26

when removing an electron breaks into a new shell, there will be a large increase in IE bc atomic radius & shielding both decrease

Question 27

trends in 1st IE across period?

Answer 27

• 1st IE increases
• NC increases
• AR decreases
• S stays same
• e- more strongly attracted to nucleus, more energy needed

Question 28

trends in 1st IE down group?

Answer 28

• IE decreases
• NC increases (eventho), Ar & S increase (also)
• e- weakly attracted to nucleus, less energy

Question 29

what is ionisation energy?

Answer 29

measures how easily an atom loses electrons to form positive ions

Question 30

successive IEs allow predictions to be made about?

Answer 30

• the number of electrons in the outer shell
• the group of the element in the periodic table
• the identity of an element

Question 31

PD structure: elements are arranged in order of?

Answer 31

increasing atomic number

Question 32

PD structure: elements within a group have?

Answer 32

same number of electrons in outer shell so
similar chemical properties
as chemical reactions involve outer shell electrons

Question 33

PD structure: s block?

Answer 33

• Groups 1,2 and He

- highest energy electron is held in an s block

Question 34

PD structure: p block?

Answer 34

• groups 3-8

- highest energy electron held in p block

Question 35

PD structure: d block?

Answer 35

• Period 4: Sc to Zn

- Period 5: Y to Cd

Question 36

PD structure: what are metalloids?

Answer 36

elements that touch the stepline between metals and non-metals
- show both metallic & non- metallic properties

Question 37

PD structure: why is hydrogen an unusual case?

Answer 37

• non metal, often included in G1 as has 1 electron in outer shell

Question 38

what is ionisation energy?

Answer 38

the energy required to completely remove an electron from an atom of an element

Question 39

general trends in IE across a period and group?

Answer 39

• Period: increase

- group: decrease