Transition Elements

Question 1

d block elements

Answer 1

Elements with their highest energy electron in the d subshell

Question 2

Transition element

Answer 2

A d block element which forms at least 1 ion with a partially filled d-orbital

Question 3

Properties of transition elements

Answer 3

• Have variable oxidation states
• form coloured compounds
• Catalytic properties
• Form complex ions
• Typical metal properties: malleable, ductile, shiny, conductors, h.m.p and h.b.p

Question 4

Exceptions to filling subshells of transition elements

Answer 4

Chromium and copper

Cr- Instead of 3s4, 4s2 –> 3s5, 4s1 (1 (single) electron in each 3s orbital means more stability)
Cu- Instead of 3s9, 4s2 –> 3s10, 4s1 (full 3d subshell means more stability)

Question 5

How to draw energy electron configuration boxes

Answer 5

Number of boxes for each subshell: Number of electrons the subshell can carry divided by 2

1s: 1 box
2s: 1 box
2p: 3 boxes
3s: 1 box
3p: 3 boxes
3d: 5 boxes

Question 6

What aren’t transition elements and why?

Answer 6

Scandium- only forms Sc3+, which has an empty d subshell

Zinc- only forms Zn2+, which has a full d subshell

Question 7

Variable oxidation states
Examples of 4 transition elements

Answer 7

Transition elements form ionic compounds with more than 1 oxidation state

Question 8

Transition elements form coloured compounds

Answer 8

Colour of a transition element compound varies with different oxidation states.

Question 9

Transition elements as catalysts:
Why
Hazards
Examples

Answer 9

Good catalysts as they can change oxidation state by losing or gaining electrons. They speed up reactions by transferring electrons.

Increased toxicity:
- Copper long term exposure damages liver and kidneys
- Manganese exposure causes psychiatric problems.

Heterogenous:
Haber process: Fe
Contact process: V2O5
Hydrogenation of alkenes: Ni catalyst
Decomposition of hydrogen peroxide: MnO2

Homogenous:
Zinc and acid reactions: CuSO4 catalyst

Question 10

Transition elements form complex ions:

Complex ion definition
Ligand definition

Coordinate bond definition

Coordination number definition

Answer 10

A complex ion is a central transition metal ion surrounded by ligands bonded by coordinate bonds.

Ligand is a molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond.

Dative covalent bond

Number of coordinate bonds attched to central metal ion.

Question 11

Monodente ligand
Bidente ligand

Answer 11

A ligand that donates 1 lone pair of electrons to the central metal ion.
Ligands that donate 2 pairs of electrons to the central metal ion, forming 2 coordinate bonds.

Question 12

What affects shape of complex ions

Answer 12

Coordination number and size of ligands

Question 13

Shape of complex ions (coordination number)

Answer 13

Coordination number of:
6- Octahedral shape, 90 degrees
4- Tetrahedral shape, 109.5 degrees or square planar, 90 degrees

Question 14

Name of complexes with:
- octahedral shape
- tetrahedral or square planar shape

Answer 14

• six-coordinate complexes
• four-coordinate complexes

Question 15

How to find oxidation state of metal in a complex ion

Answer 15

Total oxidation state of metal= total oxidation state- total oxidation state of ligands

Question 16

When does cis-trans isomerism occur
When does optical isomerism occur

Answer 16

In octahedral and square planar complex ions
In octahedral complexes with 2 or more bidente ligands

Question 17

Cis-platin

Answer 17

A complex of Pt(II) metal ion with 2 Cl- ligands and 2 NH3 ligands in a square planar shape
Used as an anti-cancer drug:

• Chloride ligands are easy to displace, so detach from complex.
• Complex bonds to 2 nitrogen atoms on DNA molecule of cancerous cell
• Prevents cancerous cell from reproducing by division and cell will die.
• However, cisplatin can also affect healthy cells, e.g., blood, which can suppress immune system. May also causes damage to kidneys.

Question 18

Ligand substitution reaction definition

Answer 18

Reaction where 1 ligand in a complex ion is replaced by another ligand

Question 19

Bonding in haemoglobin

Answer 19

Haemoglobin contains Fe2+ ions.
Fe2+ has 6 ligands: 5 Nitrogen ligands and 1 H2O ligand. When oxygen concentration is high, O2 substitutes the H2O, forming oxyhaemoglobin.

Question 20

What happens when carbon monoxide is inhaled?

Answer 20

In presence of CO, the H2O ligand is substituted for CO, which is a strong ligand and does not readily exchange with O2. This means haemoglobin can no longer transport O2 around the body.

Question 21

Oxidation of of Fe2+ to Fe3+ colour change? Conditions?

Reduction of Fe3+ to Fe2+ colour change? Conditions?

Answer 21

Purple MnO4 - to colourless Mn2+
H+/MnO4 -

yellow Fe 3+ to pale-green Fe2+
I–

Question 22

Oxidation of Cr 3+ to Cr2O7 2- colour change?
Conditions?

Reduction of Cr2O7 2- to Cr 3+ colour change?
Conditions?

Answer 22

H2O2/OH–

Zn/H+

Question 23

Reduction of Cu2+ to Cu+ colour change?
Conditions?

Wats happens to Cu+ later

Answer 23

Colour change-
I-

Cu+ is unstable and in aqeous solutions with hot dilute H2SO4 it spontaneously disproportionates to produce Cu and Cu2+

Question 24

How can transition element ions be identified?

Answer 24

Using NaOH or NH3, which form coloured precipitates.
Cu2+- blue preciptate
Fe2+ green precipitate
Fe3+ orange precipitate
Mn2+ pink precipitate
Cr3+ grey- green precipitate

Question 25

How can ligands be identified?

Answer 25

carbonate test, sulfate test, halide test, NH4+ test

Question 26

Why is alkaline solution sometimes added in redox reactions with transition metals?

Answer 26

Transition metals with low oxidation states are more easily oxidised in alkaline solution than acidic solution.
(as its easier to remove electron move negatively charged ion)(becomes -ve when alkaline added)