5.3.1: Transition elements

Question 1

Transition metal

Answer 1

a metal that forms 1 or more ions with an incomplete d subshell.

Question 2

In transition metals, the 4s is higher/lower in energy than the 3d

Answer 2

Higher

Question 3

Which subshell are e- lost from first?

Answer 3

4s

Question 4

Examples of atoms with incomplete 4s subshell

Answer 4

Cr = [Ar]3d⁵4s¹
Cu = [Ar]3d¹⁰4s¹

Question 5

Properties of transition metals

Answer 5

• Form coloured compounds

* Variable valency

Question 6

Variable valency

Answer 6

Ions with variable oxidation states

Question 7

Coordination number

Answer 7

the number of dative covalent bonds that can form with the central metal ion
NOT THE NUMBER OF LIGANDS

Question 8

Ligand

Answer 8

an atom/group of atoms that can donate a lone pair of electrons to form a dative covalent bond to the central metal ion

Question 9

Complexes with different coordination numbers

Answer 9

Most = 6
However
tetrahedral = 4
square planar complexes = 4

Question 10

Types of sterioisomerism visible in complex ions

Answer 10

1) Optical isomerism - bidentate ligands

2) E/Z isomerism - octahedral/square planar complexes

Question 11

What is the formula of a transition metal in aqueous solution?

Answer 11

[M(H₂O)₆]ⁿ⁺

Question 12

Which transition metal do not substitute further in excess NaOH?

Answer 12

• Iron (II)
• Iron (III)
• Manganese(II)
• Copper (II)

Question 13

Which transition metals do substitute further in excess NH₃?

Answer 13

• Copper (II) and Chromium (III)

Question 14

What is the formula and colour of the precipitate formed when Iron (II) reacts with NaOH or NH₃? (the complex is the same for both)

Answer 14

[Fe(OH)₂(H₂O)₄]

Pale green solution turns to green precipitate (darkens on standing)

Question 15

What is the formula and colour of the precipitate formed when Iron (III) reacts with NaOH or NH₃? (the complex is the same for both)

Answer 15

[Fe(OH)₃(H₂O)₃]

Yellow solution to orange precipitate that darkens on standing

Question 16

What is the formula and colour of the precipitate formed when Mn (II) reacts with NaOH or NH₃? (the complex is the same for both)

Answer 16

[Mn(OH)₂(H₂O)₄]

Pale pink solution to buff solution which darkens on standing

Question 17

What is the equation for Mn(II), Cu(II) or Fe(II) reacting with NaOH?

Answer 17

[M(H₂O)₆]²⁺ + 2OH⁻ –> [M(OH)₂(H₂O)₄] + 2H₂O

Question 18

What is the equation for the reaction of Fe(III) with NH₃?

Answer 18

[Fe(H₂O)₆]³⁺ + 3NH₃ –> [Fe(OH)₃(H₂O)₃] + 3NH₄⁺

Question 19

Which transition metal substitutes further in excess NH₃ but not in excess NaOH?

Answer 19

Copper (II)

Question 20

Which transition metal substitutes further in both excess NH₃ and NaOH?

Answer 20

Chromium (III)

Question 21

What is the formula and colour of the precipitate formed when copper(II) reacts with NaOH?

Answer 21

[Cu(OH)₂(H₂O)₄]

Pale blue solution to blue precipitate

Question 22

What is the equation for the reaction of Cu(II) with NH₃?

Answer 22

[Cu(H₂O)₆]²⁺ + 2NH₃ –> [Cu(OH)₂(H₂O)₄] + 2NH₄⁺
This reacts further with excess
[Cu(OH)₂(H₂O)₄] + 2NH₃ –> [Cu(NH₃)₄(H₂O)₂]²⁺ + 4H₂O

Question 23

What happens when NaOH reacts with chromium(III)?

Answer 23

[Cr(H₂O]³⁺ + 3OH⁻ –> [Cr(OH)₃(H₂O)₃] + 3H₂O
green solution to green precipitate
Reacts with excess NaOH
+ 3OH⁻ –> Cr(OH)₆³⁻ which is a dark green solution

Question 24

What happens when NH₃ reacts with chromium(III)?

Answer 24

[Cr(H₂O]³⁺ + 3NH₃ –> [Cr(OH)₃(H₂O)₃] + 3NH₄⁺
Green solution to green precipitate
Reacts with excess NaOH
+ 3NH₃ –> [Cr(NH₃)₆]³⁺ which is a purple solution