1. Title: Lesson 5 First Row d-Block
Learning Objectives:
Describe the properties of transition metals

2. Refresh By reference to the structure and bonding in NaCl and SiCl4:
State and explain the differences in electrical conductivity in the liquid state.
Predict an approximate pH value for the solutions formed by adding each compound separately to water. Explain your answer.

3. The Traditional Based on Mendeleev’s work. Easiest to use and display.

4. First row d-block elements
A transition elements can be defined as different from ‘d block elements’:
‘A transition element is an element that forms at least one stable ion with a partially filled d subshell’
For example, Cu2+: 1s2 2s2 2p6 3s2 3p6 (4s0) 3d9
Small range in atomic radii
 similar properties
Why is the range small?
We need to look at the electron configuration…

5. Decreasing atomic radii due to small increase in effective nuclear charge.
Increase in nuclear charge from added proton is offset by addition to the electron in the 3d inner shell – SHIELDING! (Without the shielding the decrease in atomic radii would be even more!)
Small range of ionisation energies because electrons are removed from the 4s shell.
Notice Cr and Cu – more stable to have half filled and filled 3d subshells respectively…

7. Solution

8. Properties of Transition Metals
Physical Properties
Chemical Properties
High electrical and thermal conductivity
Form compounds with more than one oxidation number
High melting point
Form a variety of complex ions
Malleable
Form coloured compounds
High tensile strength
Act as catalysts
Ductile
Iron, cobalt and nickel are ferromagnetic
Other things to note:
Physical properties can be explained in terms of the strong metallic bonding
3d and 4s electrons are close in energy, so are all involved in the bonding – they form part of the delocalised sea of electrons which holds the lattice together.

9. Scandium and Zinc
Although in the first row of the d-block, these are not transition metals.
To understand why, write the full electron configuration for:
Sc and Sc3+
Zn and Zn2+
However, please note that for our syllabus we count Scandium as a transition metal!

10. Zinc is not a transition metal...
‘A transition element is an element that forms at least one stable ion with a partially filled d subshell’
WHY???
Only ion it forms is Zn2+ ion
This means that 2 electrons are removed from the 4s shell
A fully filled 3d shell will be left
ALSO...
Does not form coloured compounds/solutions.

11. Variable Oxidation Number of Transition Elements
Comparison between group 2 and Transition Metals:
Ca only has oxidation state of 2+
Titanium shows +4, +3 and + 2 states
Can you relate the oxidation states formed to the pattern in successive ionisation energy? (HINT: Look at the jumps in energy...)

12. Variable Oxidation Number of Transition Elements
Comparison between group 2 and Transition Metals:
Ca only has oxidation state of 2+
Titanium shows +4, +3 and + 2 states
Can you relate the oxidation states formed to the pattern in successive ionisation energy?
Ca3+ would be unstable as 3rd electron would be removed from the 3p orbital...
Successive IE for Ti is more gradual as 3d and 4s are close in energy hence can make
+2, +3 and +4 oxidation states. No +5 as this would mean removing from 3p as well.

13. Oxidation States of d Block Elements
States respond to 3d and 4s electrons in bonding...
States highlighted blue are the more common ones
All transition metals show both 2+ and 3+ oxidation states
Note: Unlike other groups, electrons are not removed to in order to generate the nearest stable noble gas configuration...
M3+ Ions more common from Sc to Cr
M2+ Ions more common from Mn to Zn

14. High Oxidation States
Oxidation of above 3+ generally show covalent character
High charge means large charge density
They polarise negative ions
Increases covalent character of the compound
Think about electro- negativities to explain why large charge density will polarise ions…

15. Variable oxidation numbers (ions)
Transition metals have large numbers of electrons in d-orbitals,
This means the amount of energy required to remove the second electron is not much different to that required to remove the first and so on.
Some common oxidation states we need to know:
All of them in the +2 oxidation state
Cr(III), Cr(VI)
Mn(IV), Mn(VII)
Fe(III)
Cu(I)
Task: select 4 of these and write the electron configuration

17. Solutions