HL Questions on chapter 3

13.1 Periodic trends Na-> Ar (the third period)

1. Which are the oxides in the third period ?

2. What is the molecular structure of these oxides ?

3. Which oxides are basic and acidic ?

4. What is the conductivity of the oxides ?

5. What is the melting point of the oxides ?

6. What chemical reactions happen when you put the oxides in water ?

7. Which are the chlorides in the third period ?

8. What is the molecular structure of these chlorides ?

9. What is the conductivity of the chlorides ?

10. What is the melting point of the chlorides ?

11. What chemical reactions happen when you put the chlorides in water ?

d-block elements

12. What are the characteristics of d-block elements ?

13. What are the oxidation states of the d-block elements ?

14. What is a ligand ?

15. What is a complex ion ?

16. What causes the colours of the transition metals ?

17. Why are d-block elements good catalysts ?

Download notes on periodicity.

Go back to the IB chemistry page

Go to the IB physics page























Non-metals -> Acidic oxides
Metals -> Basic oxides
Metalloids -> Amphoteric (both acidic & basic) oxides.


Conductivity : For ionic solutions (Na2O->Al2O3) conductivity is due to ions in solution/molten state. SiO2 is network covalent, hence has no free charged particles, therefore has no significant conductivity. Others are covalent molecules and do not conduct.



Melting point : Stronger bonds are created when atoms can be arranged in a simple structure. MgO is highest, followed by Al2O3 then Na2O (The ratio between the two atoms should be as close to 1 as possible). SiO2 is network covalent, hence has a high melting point (but not as high as for ionic bonding). The final 3 decrease in melting point due to decreasing polarity of molecules (i.e. smaller dipole-dipole interactions).

Halides (Cl could be replaced with Br, I, F etc.) : Ionic Chlorides dissolve in H2O with little reaction, covalent chlorides dissolve and react to form HCl.

NaCl : NaCl + H2O -> Na+ + Cl- + H2O
Good conductivity (ionic structure) MP = 801

MgCl2 : MgCl2 -> Mg2+ + 2Cl-
Good conductivity (ionic structure) MP = 714

Al2Cl6 : Al2Cl6 + 6H2O -> 2Al(OH)3 + 6HCl
Poor conductivity (Network covalent) MP = 178

SiCl4 : SiCl4 + H2O -> Si(OH)4 + 4HCl
No conductivity (Covalent molecular) MP = -70

PCl3 : PCl3 + 3H2O -> H3PO3 + 3HCl

PCl5 : 2PCl5 + 6H2O -> 2HPO3 + 10HCl
No conductivity (Covalent molecular) MP = -112

S2Cl2 : Not required

Cl2 : Cl2 + H2O -> HCl + HClO (Exception : F2 is such a strong oxidizer : 2F2 + 2H2O -> 4HF + O2)
No conductivity (Covalent molecular) MP = -101

Melting point : For NaCl and MgCl2 MP decreases due to packing (as above), and drops again for Al2Cl6 (which is network covalent). The others are covalent molecules, and the mp decreases due to decreasing polarity (Cl2 higher due to more electrons, resulting in greater LDF ?)

























d-block elements are generally those exhibiting multiple oxidation states. Form coloured compounds. Form complex ions. Have catalytic properties.

The multiple oxidation states of the d-block elements (transition metals) are due to the proximity between the 4s and 3d sub shells (in terms of energy). All transition metals exhibit a 2+ oxidation state (both electrons being lost form the 4s) and all have other oxidation states as in the following examples:

























Ligands are the molecules which donate an electron pair to form a dative covalent bond with the central atom (thus forming a complex ion).

Complex ions are molecules which carry a charge. They are formed around a central atom, with other atoms (or molecules) donating an electron pair to form a covalent bond to this central atom.

[Fe(H2O)6]3+ : Fe is the central atom, H2O is the ligand.

[Fe(CN)6]3- : Fe is the central atom, CN is the ligand.

[CuCl4]3- : Cu is the central atom, Cl is the ligand.

[Cu(NH3)4]2+ : Cu is the central atom, NH3 is the ligand.

[Ag(NH3)2]+ : Ag is central atom, NH3 is the ligand.

























The colour in the transition metals (d-block) is predominantly due to the splitting of the d shell orbitals into slightly different energy levels. As a result, certain wavelengths of energy can be absorbed by the d-block elements (with electrons jumping between these slightly different energy levels), resulting in the complement colour being visible.

d-block elements make good catalysts due to their multiple oxidation states. This gives them the ability to react with different species and produce a path of lower activation energy, and so cause the reaction to proceed at a faster rate. Examples: