Periodicity

Question 1

1st ionisation energy

Answer 1

the energy required to remove 1 electron from each atom in 1 mole of gaseous atoms

Question 2

what are successive ionisation energies

Answer 2

the energy required to remove each electron in turn from each atom in 1 mole of gaseous atoms

Question 3

what is the magnitude of ionisation energy influenced by

Answer 3

nuclear charge, atomic radius, shielding

Question 4

nuclear charge

Answer 4

the greater the nuclear charge, the greater the attraction on the outer electrons so more energy is required to remove electron - larger ionisation energy

Question 5

atomic radius

Answer 5

the further the electron from the nucleus the weaker the attraction (less energy required to remove electron - smaller ionisation energy)

Question 6

shielding

Answer 6

full inner shells of electrons exert a repelling effect on the outer electrons as they are both negatively charged. this reduces the attraction between the nucleus and outer electron (less energy required to remove electron - smaller ionisation energy)

Question 7

successive ionisation energies

Answer 7

steady increase in amount of energy needed to remove successive electrons

Question 8

when an electron is removed

Answer 8

the remaining electrons are pulled closer to nucleus - the nucleus attracts remaining electrons more strongly so more energy is needed to remove them (higher i.e)

Question 9

inner electron removed

Answer 9

there is a big jump in i.e when an electron is removed from an inner shell. the inner electron is much closer to the nucleus and is less shielded than the outer electron, so experiences a greater attraction and has a higher i.e

Question 10

1st and 2nd i.e and 9th and 10th i.e

Answer 10

this shows clearly where an electron is being removed from an inner shell

Question 11

1st i.e trend down a group

Answer 11

• nuclear charge increases
• atomic radius increases so electron is further from nucleus
• shielding increases as number of full inner shells increases
• increase in distance and shielding outweigh increased nuclear charge
• nuclear attraction on outer electron decreases
  so first ionisation energy DECREASES

Question 12

1st i.e general trend across period

Answer 12

• nuclear charge increases
• atomic radius decreases so outer electron is closer to the nucleus
• shielding stays same as electrons are in same shell
• nuclear attraction on outer electron increases
• first ionisation energy INCREASES

Question 13

decrease between groups 2 and 3 (Be and B)

Answer 13

• Be: 1s2 2s2 B: 1s2 2s2 2p1
• 2p orbitals have slightly more energy than 2s
• s electrons provide slightly greater shielding of the p electron
• less energy needed to remove outer electron from B than Be despite increase in nuclear charge

Question 14

decrease between groups 5 and 6 (N and O)

Answer 14

• N: 1s2 2s2 2p3 O: 1s2 2s2 2p4
• spin pairing occurs in 2p subshell of oxygen
• paired electrons in a 2p orbital of oxygen repel eachother
• less energy needed to remove outer electron from O than N despite increased nuclear charge

Question 15

what creates nuclear charge

Answer 15

more protons in a nucleus leading to a greater attraction between nucleus and electrons

Question 16

what is an orbital

Answer 16

the space where an atom can hold two electrons with opposite spins

Question 17

what did dmitri mendeleev do

Answer 17

in 1869 he noticed that if the elements are arranged in ascending order of atomic mass with new rows started at the correct points then elements with similar properties are grouped in vertical columns

Question 18

group number

Answer 18

number of outer shell electrons

Question 19

period number

Answer 19

number of shells of electrons

Question 20

elements in the same group…

Answer 20

have similar chemical properties because they have the same number of electrons in their outer shells

Question 21

number of period

Answer 21

gives number of highest energy electron shell

Question 22

what is periodicity

Answer 22

the repeating trends in physical and chemical properties across the periods of the periodic table

Question 23

periodicity atomic radii decrease across a period…

Answer 23

• nuclear charge increases
• same number of shells of electrons so no increased shielding
• nuclear attraction increases, outer electrons attracted more strongly to nucleus, so pulled in closer and radius is made smaller

Question 24

periodicity atomic radii increases when descending a group…

Answer 24

• more shells of electrons
• increase in shielding outweighs increased nuclear charge
• nuclear attraction on the outer electrons decreases so atomic radius increases

Question 25

on crossing a period what are formed

Answer 25

ions

Question 26

on crossing from na+ to si4+ and from p3- to cl-

Answer 26

- each have same number of electrons - increase in nuclear charge - nuclear attraction on outer e- increases - ionic radius decreases

Question 27

anions

Answer 27

larger than atoms of the same element | - have same nuclear charge holding more electrons so nuclear attraction is weaker

Question 28

cations

Answer 28

smaller than atoms of the same element - same nuclear charge holding fewer electrons so nuclear attraction is greater - also, one less shell of electrons so shielding is reduced

Question 29

melting point of elements

Answer 29

- depends on the strength of the bonds which have to be broken - the melting points of metals are relatively high because of the strong metallic bonds that have to be broken

Question 30

why do melting points increase from Na to Al

Answer 30

- there are more outer shell electrons which can be delocalised - the charge density or the metal ion is increasing

Question 31

what type of structure is highest melting point

Answer 31

giant covalent lattices (eg silicon and carbon) due to many strong covalent bonds that have to be broken

Question 32

what type of structure is lowest melting point

Answer 32

simple molecular covalent - bonding between molecules - weak id:id attractions - the strength of these depends on the total number of electrons in each molecule - s8 > p4 > cl2 > ar

Question 33

electronegativity increases across a period

Answer 33

- nuclear charge increasing so bonding electrons pulled closer to nucleus - no change in shielding - nuclear attraction on bonding electrons is greater

Question 34

diamond structure

Answer 34

- carbon forms 4 covalent bonds with other carbon atoms - tetrahedral arrangement - giant covalent network - strong covalent bonds throughout - bond angle 109.5°

Question 35

diamond physical property

Answer 35

- very high mp due to strong covalent bonds that must be broken - strong and hard due to covalent bonds that are strong and need to be broken (insoluble) - do not conduct (no free electrons or ions)

Question 36

uses of diamond

Answer 36

in tools for polishing and cutting

Question 37

graphene structure

Answer 37

- carbon forms 3 covalent binds with other carbon atoms - 4th electron of each carbon is delocalised - single sheets of interlocked hexagons - one atom thick - strong covalent bonds throughout

Question 38

physical properties of graphene

Answer 38

- conducts electricity as 4th electron can move | - high strength due to network of covalent bonds

Question 39

structure of buckmindsterfullerene

Answer 39

-60 carbon atoms, carbon atom at each corner of 20 hexagons and 12 pentagons

Question 40

buckminsterfullerene physical properties

Answer 40

semi conductors

Question 41

uses buckminsterfullerene

Answer 41

catalysts lubricants nanotubes

Question 42

graphite structure

Answer 42

- carbon forms 3 covalent bonds with other C atoms - 4th electron delocalised - layers of interlinked hexagons - bonds 120° - strong covalent bonds each layer but weak london forces between these layers

Question 43

physical properties graphite

Answer 43

- very high mp - strong cb to break soft solids -> layers can slide as only weak forces between them - insoluble strong cb need to be broken - conducts due to electrons able to move within layers

Question 44

uses of graphite

Answer 44

``` dry lubricants (slippery) electrodes (conducts) ```

Question 45

qualitative analysis of carbonate ions co32-

Answer 45

- add dilute nitric acid - effervescence may mean carbonate is present co32- + 2h+ -> co2(g) + h2o (l) - bubble through limewater (saturated ca(oh)2) and will turn cloudy results in caco3

Question 46

qualitative analysis of sulphate ions so42-

Answer 46

- add nitric acid and barium nitrate solution (allows halide ion test to be done) - white ppt of barium sulphate shows present sulphate ions ba2+ + so42- -> baso4

Question 47

qualitative analysis of halide ions cl- br- i-

Answer 47

add nitric acid and silver nitrate to aqueous solution - white for cl- (soluble in dilute nh3 aq) - cream for br- (soluble in conc. nh3 aq) - yellow for i- (insoluble in conc. nh3 aq)