3 Periodicity

Question 1

where in the periodic table is the largest atom

Answer 1

bottom left

(to the right, nuclear charge incr and hence greater pull)

Question 2

what is the electron shell theory

Answer 2

atomic radii decr across a period as atomic number incr

Question 3

explain shielding effect

Answer 3

electrons in the inner shells repel the electrons in the outermost shells

Question 4

ionic radius down a period

Answer 4

incr with incr NEGATIVE

decr with incr POSTIVE

so more negative is bigger

Question 5

why does ionic radius increase as charge becomes more negative

Answer 5

atoms accept more electrons, nuclear charge remains the same
= new electrons experience repulsion

Question 6

4 factors influencing ionisation energy

Answer 6

1. size of nuclear charge
2. distance of outer electrons from nucleus
3. shielding effect
4. spin-pair repulsion

Question 7

recall ionisation energy trends esp anomalies

Answer 7

theyre in 7 i think

Question 8

define electron affinity

Answer 8

(the opposite of ionisation energy)

amt of energy RELEASED when ONE MOLE of electrons is gained by ONE MOLE of atoms of an element in the GASEOUS state to form ONE MOLE of GASEOUS IONS

Question 9

electron affinities are measured under standard conditions which are ___ K and ____ kPa

Answer 9

298k (25C)

100kPa

Question 10

units for electron affinity

Answer 10

kilojoules / mole

kJ / mol

Question 11

the first electron affinity is always (exo/endo thermic)

Answer 11

EXOthermic

Question 12

why can second electron affinity by endothermic

Answer 12

energy is required to overcome repulsion between electron and negative ion

Question 13

the most exothermic electron affinities belong to ….

Answer 13

group 17! they also have the highest electronegativities

Question 14

what elements are missing from electron affinity charts

Answer 14

noble gases! they do not form negative ions

Question 15

which 2 groups does electron affinity peak

Answer 15

2 and 5

Question 16

electron affinities (incr/decr) down a grp

Answer 16

decrease – less exothermic

• atoms larger = incr shielding = decr effective nuclear charge

Question 17

why is the electron affinity for fluorine less than expected?

Answer 17

fluorine is a small stom

additional electron in 2p subshell = considerable repulsion w other valence electrons

Question 18

define electronegativity

Answer 18

ability of an atom to attract a pair of electrons towards itself in a covalent bond

Question 19

what is the most electronegative atom

Answer 19

fluorine

(4.0 on the Pauling scale!)

Question 20

2 factors affecting electrongeativity

Answer 20

nuclear charge
- more protons = incr nuclear attraction = more electroneg

atomic radius
- closer = more strongly attracted = incr electroneg

Question 21

electrongeativity down a group

Answer 21

decrease down a group
- nuclear charge incr BUT extra shell = shielding
- incr dist
decr effective nuclear charge

Question 22

how does electronegativity change across a period

Answer 22

increases

protons added = incr nuclear charge
same shielding

incr attraction
smaller atomic radii

Question 23

the larger the electrongeativity, the _____ the atomic radii

Answer 23

smaller

Question 24

electronegativity vs electron affinity

Answer 24

chemical character, only covalent bonds!

thermodynamic value measurable – formation of negative ions

Question 25

low _________ ________ and low __________________ of metals can account for delocalisation of electrons

Answer 25

ionisation energies (less energy req to seperate)

electronegativities (Attraction low)

Question 26

high __________ and high __________ explain tendency to form covalent bonds in nonetals

Answer 26

electronegativity

electron affinity

Question 27

change in acid-base character across a period

Answer 27

basic –> amphoteric –> acidic

Question 28

aluminum oxide is acid/base?

Answer 28

amphoteric! can act as both

Question 29

why are metal oxides basic

Answer 29

largest difference in electronegativity with oxygen – forms ionic bond

eg Na and Mg – purely ionic bonding = alkaline

oxide ions become hydroxide ions

Question 30

why are nonmetal oxides acidic

Answer 30

close electrongeativity to oxygen = covalent bond

forms acid, donates H+

Question 31

reaction of NO2 with water?

Answer 31

2NO2 + H2O –> HNO3 + HNO2

Question 32

reaction of SO2 and SO3 in water?

Answer 32

SO2 + H2O –> H2SO3
SO3 + H2O –> H2SO4

Question 33

more electronegative = more/less ionic?

Answer 33

less ionic (electroneg is for COVALENT!)

Question 34

transition metals have an incomplete ____ subshell

Answer 34

d

Question 35

within the d block elements, which ones are transition elements?

Answer 35

exclude the last group of both sides
- they only form one ion with empty/complete d subshell

Question 36

transition elements definition

Answer 36

incomplete d subshell

form at least one stable cation with an incomplete d subshell

Question 37

between 3d and 4s subshells, remove electrons from? when forming cations

Answer 37

4s

Question 38

5 characteristics of transition elements

Answer 38

1. variable oxidation states
2. form complex ions
3. form coloured compounds
4. behave as catalysts
5. have magnetic properties

Question 39

what is a ligand

Answer 39

a molecule / ion surrounding the central metal atom/ion

Question 40

colours of…
[Cr(OH)6]3- complex
[Cr(NH3)6]3+ complex

Answer 40

dark green

purple

Question 41

what makes transition elements good catalysts

Answer 41

variable oxidation states

Question 42

why do transition elements lose electrons from the 4s subshell first

Answer 42

when orbitals are occupied, repulsion betw electrons

pushes 4s to higher energy state (slightly higher than 3d)

= +2 is a common oxidation state

Question 43

describe transition metals with oxidation state +3 and above

Answer 43

polarising

high degree of covalent charater (bonds)

high charge density – pull electrons towards themselves