Transition Elements

Question 1

TRANSITION ELEMENTS

Answer 1

d block elements that have an ion with an incomplete d sub-shell.
This rules out Sc³⁺ and Zn²⁺

Question 2

Characteristics of transition metals

Answer 2

• variable oxidation states
• catalytic activity
• formation of complexes
• formation of coloured compounds

Question 3

Types of reaction

Answer 3

Redox
Ligand Substitution
Redox

Question 4

Electron arrangement exceptions

Answer 4

Cr = 3d⁵
Cu = 3d¹⁰

Question 5

Examples of transition elements being used as catalysts.

Answer 5

• Fe is a catalyst in the Haber process
N₂ + 3H₂ → 2NH₃

• Ni is a catalyst in the hydrogenation of alkenes
R=R + H₂ ⇌ R-R

Question 6

Formation of coloured ions

Answer 6

Cr₂O₇²⁻ = orange
CrO₄⁻ = yellow
MnO₄⁻ = purple
Mn²⁺ = pale pink
Cu²⁺ = blue
Co²⁺ = pink
Fe²⁺ = pale green
Fe³⁺ = yellow-brown

Question 7

Cis Platin

Answer 7

• Anti-cancer drug
• Binds to DNA and prevents it replicating
• Pt attached to 2Cl and 2NH₃ (square planar)

Question 8

Haemoglobin

Answer 8

• O₂ binds to Fe²⁺
• When required, O is released/substituted
• Stability constant of CO is greater than O₂
• Stronger coordinate bond with CO

Question 9

Shapes of molecules

Answer 9

Octahedral, 90°, 6 co-ordinate bonds
Tetrahedral, 109.5°, 4 co-ordinate bonds
Square planar, 90°, 4 co-ordinate bonds

Question 10

Precipitation reactions

Answer 10

Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂ (s) (blue → blue)
Co²⁺(aq) + 2OH⁻(aq) → Co(OH)₂ (s) (pink → blue)
Fe²⁺(aq) + 2OH⁻(aq) → Fe(OH)₂ (s) (pale green → green)
Fe³⁺(aq) + 3OH⁻(aq) → Fe(OH)₃ (s) (yellow → brown)

Question 11

Cu²⁺ with ammonia (drop wise)

Answer 11

NH₃ + H₂O → NH₄⁺ + OH⁻
NH₃ is a source of OH⁻
Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂ (s)
blue → blue

Question 12

Cu²⁺ with ammonia (large excess)

Answer 12

[Cu(H₂O)₆]²⁺(aq) + 4NH₃(aq) ⇌ [Cu(NH₃)₄(H₂O)₂]²⁺(aq) + 4H₂O(l)
blue solution → dark blue solution

Question 13

Cu²⁺ with HCl (large excess)

Answer 13

[Cu(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌ [CuCl₄]²⁻(aq) + 6H₂O(l)

blue solution → yellow-green solution

Question 14

Co²⁺ with HCl (large excess)

Answer 14

[Co(H₂O)₆]²⁺(aq) + 4Cl⁻(aq) ⇌ [CoCl₄]²⁻(aq) + 6H₂O(l)

pink solution → blue solution

Question 15

Stability constants, Kstab

Answer 15

• Do not include H₂O in the equation

* Large Kstab = more stable complex ion

Question 16

d-block ELEMENTS

Answer 16

The highest energy sub-shell is a d sub-shell.

Question 17

LIGAND

Answer 17

A molecule or ion that can donate a pair of electrons to a transition metal ion to form a coordinate bond.

Question 18

COMPLEX ION

Answer 18

A transition metal ion bonded to one or more ligands by coordinate bonds (dative covalent bonds).

Question 19

COORDINATE BOND

Answer 19

A shared pair of electrons in which one of the bonded atoms provides both electrons for the shared pair.

Question 20

COORDINATION NUMBER

Answer 20

The total number of coordinate bonds formed between a central metal ion and its ligands.

Question 21

BIDENTATE LIGAND

Answer 21

A ligand which can donate two lone pairs of electrons to a metal ion to form two coordinate bonds.

Question 22

LIGAND SUBSTITUTION

Answer 22

A reaction in which one ligand in a complex ion is replaced by another ligand.

Question 23

STEREOISOMERS

Answer 23

Species with the same structural formula, but with a different arrangement of the atoms in space.

Question 24

OPTICAL ISOMERS

Answer 24

Stereoisomers that are a pair of non-superimposable mirror images of each other.

Question 25

Why is Platin a neutral complex?

Answer 25

Pt is 2⁺ and 2 x Cl is 2⁻

Question 26

Describe the bonding in Platin.

Answer 26

Ligand donates an electron pair to metal/Pt/forms a coordinate bond to the metal