periodicity– transition metals

Question 1

what are transition metals? (short defin.)

Answer 1

• a d-block element that forms 1 or more stable ions w partially filled d subshell

Question 2

what are the exceptions in the transition metals?

Answer 2

Zn, Sc3+, Cu+

Question 3

why is Zn not considered a transition metal?

Answer 3

• it forms only 1 ion, Zn2+
• Zn2+ has a fully filled d subshell

Question 4

why is Sc3+ not considered a transition metal?

Answer 4

it has no e- in its d subshell

Question 5

why is Cu+ not a transition metal?

Answer 5

it has a fully filed d subshell

Question 6

____ orbitals are filled before ___

Answer 6

4s, 3d

Question 7

in transition metals, 4s is filled before 3d except for…

Answer 7

Cr and Cu

Question 8

why do Cr and Cu not have a fully filled 4s orbital?

Answer 8

• Cr -> 3d orbitals are half filled and more stable than fully filled 4s
• Cu -> 3d orbitals are fully filled and stable

Question 9

d-block metals have a [higher/lower] m.p. compared to s-block metals

Answer 9

higher

Question 10

is the atomic radii of transition metals generally larger or smaller than s-block metals?

Answer 10

smaller

Question 11

transition metals are [more/less] dense than s-block metals

Answer 11

more

Question 12

_____ metals are poorer conductors of electricity compared to ______ metals

Answer 12

s-block, d-block

Question 13

why is the atomic and ionic radii of d-block elements smaller than s-block elements?

Answer 13

• d subshell SE not as effective as p subshell
  
  • as d subshells are more diffused
• valence shell for d-block elements exp greater nuclear attraction -> smaller radii

Question 14

how does the atomic radius change across the period and why?

Answer 14

• decr slightly:
  
  • due to nuclear charge incr slightly -> SE incr slightly -> ENC increases slightly
  • thus radius decr slightly

Question 15

what is the trend for ionisation energies across the period?

Answer 15

• incr slightly

Question 16

why does ionisation energies incr slightly from s-block to d-block

Answer 16

• p subshell provides better shielding than d subshell
  
  • d subshells more diffused
• valence shell of d-block elements exp greater nuclear attraction
• thus greater IE for d-block

Question 17

there is a ______ incr from 1st to 2nd IE, and a _______ incr from 2nd to 3rd IE

Answer 17

small, large

Question 18

there is a small incr from 1st to 2nd IE because…

Answer 18

both first and second electrons are removed from the same orbital, 4s

Question 19

the large increase from 2nd to 3rd IE in d block elements is because…

Answer 19

• third electron is removed from 3d subshells
• SE decr -> ENC incr

Question 20

why is the 2nd IE of Mn lower than that of Cr?

Answer 20

• 2nd e- removed from Mn is 4s
• 2nd e- removed from Cr is 3d
• 4s is in outer shell -> experiences weaker ENC

Question 21

why is the 3rd IE of Mn>Fe?

Answer 21

• Fe = 3d6
• electron removed is in the same orbital as another electron
  
  • inter-electronic repulsion
• thus less energy req

Question 22

why do trans elements have greater m.p. than s-block?

Answer 22

• 3d + 4s energies are relatively similar
  
  • TM can lose more valence e-
  • thus more delocalised e-
• stronger electrostatic FOA btw metal cation and sea of delocalised e-
• TMS have stronger metallic bonding -> higher m.p.

Question 23

what is the trend of m.p. across the d-block?

Answer 23

incr then decr

Question 24

why does m.p. increase from Sc to Cr?

Answer 24

• Cr has 5 unpaired e- (3d)
• Sc has 1 unpaired e- (3d)
• Cr has more unpaired e- in 3d subshell
• thus stronger metallic bonding

Question 25

why does m.p. decrease from Fe to Zn?

Answer 25

- less unpaired e- in 3d subshell - weaker metallic bonding

Question 26

why are d-block elements more dense than s-block

Answer 26

- stronger metallic bond strength - smaller atomic radii thus more closely packed

Question 27

why does Mn have a lower m.p.?

Answer 27

Cr: 4s1 3d5 Mn: 4s2 3d5 - Mr has less unpaired e- - thus weaker metallic bonds - lower m.p.

Question 28

the density of d-block elements ______ across the period as...

Answer 28

incr - atomic radii decr slightly - more atoms can be packed closely together

Question 29

what are the two forms of magnetism?

Answer 29

paramagnetism, diamagnetism

Question 30

paramagnetism is when..

Answer 30

an ion, molecule, atom has unpaired e-

Question 31

paramagnetic substances are [attracted/repelled] by a magnetic field, as...

Answer 31

attracted - unpaired e- give rise to a magnetic field that can be affected by external magnetic field

Question 32

diamagnetism is caused by ______ e-.

Answer 32

paired

Question 33

how do diamagnetic substances respond to a magnetic field?

Answer 33

they are repelled

Question 34

how do you find the maximum oxidation state of a TM?

Answer 34

no. 4s e- + no. 4d e-

Question 35

what is a catalyst?

Answer 35

a substance that **incr the ROR** by **providing an alternative rxn pathway** that **lowers Ea**

Question 36

what are the two types of catalysts?

Answer 36

- homogenous - heterogenous

Question 37

heterogenous catalysts are in a ______ ________ as the reactants

Answer 37

diff phase

Question 38

how do TMs act as heterogenous catalysts? (3)

Answer 38

1. reactants adsorb to e active sites of catalyst - weakens the covalent bonds within the rxt molecules - lowers Ea for the rxn 2. it incr surface conc and ensures proper orientation for the rxn 3. products deabsorb fr e active site -> freeing up active sites

Question 39

why can TMs act as homogenous catalysts? (1)

Answer 39

- they can form variable oxidation states - i.e. they can be easily converted fr one ox state to another

Question 40

what are ligands? (defin.)

Answer 40

an anion or molecule that has at least one lone pair of e- that can be donated into the vacant orbitals in the central metal atom

Question 41

what are complexes? (defin.)

Answer 41

a complex consists of a **central metal atom or ion** surrounded by other ions or molecules called **ligands** through **dative bonds**

Question 42

ligands act as _______

Answer 42

Lewis bases

Question 43

why can TMs form complexes? (2)

Answer 43

their metal cations have 1. high charge densities - hence high polarising power -> cations can attract lone pair of e- from ligands 2. vacant, low-lying 3d orbitals - can accept lone pair of e- donated by ligands -> dative bond formed

Question 44

ligands can be _________ charged or ___________ charged

Answer 44

neutrally or negatively

Question 45

why are ligands Lewis bases?

Answer 45

they are e- pair donors

Question 46

a ligand that forms 2 dative bonds is called...

Answer 46

bidentate

Question 47

what is ligand exchange?

Answer 47

a stronger ligand replacing a weaker ligand from a cation complex

Question 48

ligand exchange can be seen through observing a _______________

Answer 48

colour change

Question 49

why are TM complexes coloured? (short)

Answer 49

due to the presence of partially filled d-orbitals

Question 50

why are some TM complexes colourless?

Answer 50

- complexes with Sc3+ ion -> 3d subshell is empty - Zn2+ -> 3d subshell is full

Question 51

why do transition metals form coloured compounds? (4)

Answer 51

- in the presence of ligands, the d orbital splits into 2 energy levels - an e- in the lower energy level is able to be promoted to the higher energy level - by absorbing a wavelength of light in the visible region - the complimentary colour of the light absorbed is observed

Question 52

what affects the colour of complexes? (2)

Answer 52

1. nature and oxidation state of TM 2. nature of ligands

Question 53

how does the nature and oxidation state of TM affect the colour of complexes?

Answer 53

- diff no. of e- in the d orbitals repel e- of ligands to a diff extent - gives rise to diff energy gaps -> diff colour

Question 54

the nature of ligands affects the colours of complexes as...

Answer 54

diff ligands split the d-orbitals to a diff extent

Question 55

the longest wavelength is...

Answer 55

red

Question 56

what is the shortest wavelength?

Answer 56

violet