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Flashcards in KA 3: transition metals Deck (44)
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1
Q

What are d-block transition metals?

A

Metals with an incomplete d subshell in at least one of their ions

2
Q

what does the filling of d-orbitals follow?

what are the exceptions?

A

the aufbau principle

chromium and copper atoms

3
Q

what are these exceptions due to?

A

the special stability associated with the d subshell being half-filled or completely filled

4
Q

what happens when atoms from the first row of the transition elements form ions?

A

it is the 4s electrons that are lost first rather than the 3d electrons

5
Q

what can be used to determine whether oxidation or reduction has occurred?

A

changes in oxidation number of transition metal ions

6
Q

what can oxidation be defined as?

A

an increase in oxidation number

7
Q

What can reduction be defined as?

A

decrease in oxidation number

8
Q

what are compounds containing metal in high oxidation states usually classed as?

A

oxidising agents

9
Q

what are compounds containing metal in ow oxidation states usually classed as?

A

reducing agents

10
Q

an element is said to be in a particular oxidation state when…

A

…it has a specific oxidation number

11
Q

how can the oxidation number be determined?

A

-uncombined elements have an oxidation number of 0

-ions containing single atoms have an oxidation number that is the same as the charge on the ion

-in most of its compounds, oxygen has an oxidation number of −2

-in most of its compounds, hydrogen has an oxidation number of +1

-the sum of all the oxidation numbers of all the atoms in a neutral compound must add up to zero

-the sum of all the oxidation numbers of all the atoms in a polyatomic ion must be equal to the charge on the ion

12
Q

what can a transition metal have in its compounds?

A

different oxidation states

13
Q

Compounds of the same transition metal in different oxidation states may have…

A

different colours

14
Q

ligands may be…

A

negative ions or molecules with non-bonding pairs of electrons that they donate to the central metal atom ion, forming dative covalent bonds.

15
Q

What can ligands be classified as?

A

Monodentate, bidentate up to hexadentate

16
Q

what happens in the formation of a simple covalent bond?

A

each atom supplies one electron to the bond

17
Q

What is a dative covalent bond?

A

a covalent bond (a shared pair of electrons) in which both electrons come from the same atom

18
Q

how is a dative bond shown?

A

using an arrow

19
Q

what is it possible to do?

A

to deduce the ligand classification from a formula or structure of the ligand or complex

20
Q

What is the coordination number?

A

The total number of bonds from the ligands to the central transition metal

21
Q

what is a complex?

A

a transition metal surrounded by ligands

22
Q

How can names and formulae be written?

A

-ligands are listed first followed by the metal

-if there is more than one type of ligand use the usual prefixes of di,tri etc

-when listing ligands, do so alphabetically (the prefixes don’t count)

23
Q

what do the IUPAC rules cover?

A

-central metals that obey the rules

-copper (cuprate) and iron (ferrate)

-ligands, including water, ammonia, halogens, cyanide, hydroxide and oxalate

-roman numerals are shown for the oxidation state of the metal

24
Q

how do you make the formula?

A

-the complex is enclosed within square brackets

-the metal symbol is written first then the ligands in alphabetical order

-the atom bound to the transition metal should always be listed first where reasonable to do so

-the charge on the complex goes outside the brackets

25
Q

what happens if a complex is overall negative?

A

the metal name ends in “-ate”

26
Q

what happens to the name if the complex has a positive or neutral charge?

A

the name doesn’t change

27
Q

what happens to the d-orbitals in a complex of transition metals?

A

they’re no longer degenerate

28
Q

what is the splitting of the d-orbitals into higher and lower energies due to?

A

repulsion between the electrons in the approaching ligand and electrons in orbitals lying along the axes.

29
Q

what does the extent of the splitting depend on?

A

the ligands involed

30
Q

what are strong field ligands?

A

Ligands that cause a large difference in energy between subsets of d orbitals

31
Q

what are weak field ligands?

A

ligands that cause a small energy difference between subsets of d orbitals

32
Q

what is the spectrochemical series?

A

where ligands are placed in an order of their ability to split d orbitals

33
Q

the greater the splitting the greater…

A

…the energy difference between the two subsets of orbitals

34
Q

when is light absorbed?

and what does this account for?

A

When electrons in a lower energy d orbital are promoted to a d orbital of higher energy

the colour of many transition metal complexes

35
Q

if light of one colour (from the visible spec) is absorbed, what happens?

A

the complementary colour will be observed

36
Q

what can transition metals and their compounds act as?

A

catalysts

37
Q

what state are heterogeneous catalysts in?

A

a different state to the reactants

38
Q

what can heterogeneous catalysts be explained in terms of?

A

-formation of activated complexes

-the adsorption of reactive molecules onto active sites

39
Q

what is thought to allow activated complexes to form?

what does this provide?

A

The presence of unpaired d electrons or unfilled d orbitals

reaction pathways with lower activation energies compared to the uncatalysed reaction

40
Q

where does the reaction occur?

A

on the surface of the catalyst

41
Q

what happens when the reaction occurs om the surface of the catalyst?

A
  • partially filled d-orbitals can form weak temporary bonds
  • this allows new bonds to form between atoms on the surface
  • the products move away (lower activation energy pathway) and the active site on the metal can be reused
42
Q

what state are homogeneous catalysts in?

A

the same state as the reactants

43
Q

how can homogeneous catalysts be explained?

A

in terms of changing oxidation states with the formation of intermediate complexes.

44
Q

give an example of the variability of oxidation states

A

(rochelle salts experiment)