Revision:Periodicity - 13

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

13.1.1

(This seems very much like the last bit of SL, but now with explanations)

Elements on the left are metallic...right are non-metals...Al is a metalloid (semi-metal).

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

Oxide	Na2O	MgO	Al2O3	SiO2
Adding H2O			Insoluble	Insoluble
Adding HCl				No reaction
Adding NaOH	No reaction	No reaction
Nature	Basic Oxide	Basic Oxide	Amphoteric Oxide	Acidic Oxide
Conductivity	Good	Good	Good	None
Melting Point	1275	2852	2027	1610

Oxide	P4O10 (or P4O6)	SO3 (or SO2)	Cl2O7
Adding H2O
Adding HCl	No reaction	No reaction	No reaction
Adding NaOH
Nature	Acidic Oxide	Acidic Oxide	Acidic Oxide
Conductivity	None	None	None
Melting Point	24	17	-92

Explaining the physical properties

Conductivity for ionic solutions (Na2O->Al2O3) is due to ions in solution/molten state. SiO2 is network covalent - no charges therefore no significant conductivity. Others are covalent molecules therefore no conduction.

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

Halides (assuming Cl...could replace with Br, I, F etc) : Ionic Chlorides -> dissolved in H₂O with little reaction, Covalent Chlorides -> dissolve + react to form HCl.

Good conductivity (ionic structure) MP = 801

Good conductivity (ionic structure) MP = 714

Poor conductivity (Network covalent) MP = 178

No conductivity (Covalent molecular) MP = -70

No conductivity (Covalent molecular) MP = -112

S₂Cl₂ Not required

(Exception : F2 is such a strong oxidizer : )

No conductivity (Covalent molecular) MP = -101

MP - NaCl and MgCl₂ -> decreases due to packing (as above), drops to Al₂Cl₆ (network covalent). Others are covalent molecules - decreases due to decreasing polarity (Cl₂ higher due to more electrons - greater LDF ?)

13.2 D-block elements (first row)

13.2.1

Typical d-block elements are generally those exhibiting multiple oxidation states (in period 4, not Sc or Zn)

13.2.2

The multiple oxidation states of the d-block (transition metal) elements is 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...ie

V - +4, +5 (apparently we need to know only 2 of these...weird if you ask me...but include Fe...

Cr - +3, +6

Mn - +4, +7

Fe - +3

13.2.3

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

13.2.4

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. Examples...

[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

13.2.5

The color 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 color being visible.

13.2.6

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

MnO₂ in decomposition of hydrogen peroxide

V₂O₅ in the contact process

Fe in Harber process

Ni in conversion of alkenes to alkanes

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