3.1 The Periodic Table

3.1.1 : Elements increase in atomic number across each period, and down each group. The history is boring and pointless (like all history)...ignore it.

3.1.2 : Group - the columns going down. Period - the rows going across.

3.1.3 : Group = number of valence electrons in the atom. Period = number of main electron shells...s, p , d and f blocks as described above.

3.2 Physical Properties

3.2.1 :

Li->Cs (down the alkali metals) : Atomic radius increases due to increased electron shielding. Ionic radius increases due to increased electron shielding. Ionisation energy decreases due to increased electron shielding. Melting/boiling point decreases due to increased electron shielding->decreased forces. Electronegativity decreases due to increased shielding -> decreased attraction for outer electrons.

F->I (Down the halogens) : Atomic radius increases due to increased electron shielding. Ionic radius increases due to increased electron shielding. Ionisation energy decreases due to increased electron shielding. Melting/boiling point increases due to increased number of electrons->increased london dispersion forces. Electronegativity decreases due to increased shielding -> decreased attraction for outer electrons.

Na->Ar (across period 3) : Atomic radius decreases due to increased nuclear charge -> greater attraction for electrons. Ionic radius decreases Na->Al (due to increased nuclear charge) jumps Al->Si (due to reversal of ionisation direction...increased electron-electron repulsion) decreases Si->Ar (due to increased nuclear charge). Ionisation energy increases due to increased nuclear charge. Melting/boiling point increases Na->Si (due to stronger metallic bonding - more delocalized electrons then network covalent) drops Si-P (due to network->molecular covalent) increases P->S (due to increased LDF between molecules ie P₄, S₈). Drops to Cl, due to smaller molecules (Cl₂) decreases to Ar (individual atoms->fewer electrons->smaller LDF). Electronegativity increases due to increased nuclear charge -> greater attraction for electrons.

3.3 Chemical Properties

3.3.1 : Reactions of elements in the same group are similar because they have identical outer shells (ie same number of valence electrons). Generalized reactions follow :

Alkali metal (group 1) with water

2Na + 2H₂O -> 2Na⁺ + 2OH^- + H₂

Alkali metal (group 1) with Halogen

2Na + Cl₂ -heat-> 2NaCl (Na acts as a reducing agent...is oxidized, Cl₂ is reduced)

Halogen with water

Cl₂ + H₂O <=> HCl + HClO (Exception F₂ is such a strong oxidizer : 2F₂ + 2H₂O -> 4HF + O₂)

Halogen + Halide ion

	Cl-	Br-	I-
Cl2	Colorless -> Cl2	Red -> Br2	Violet -> I2
Br2	Red -> Br2	Red -> Br2	Violet -> I2
I2	Violet -> I2	Violet -> I2	Violet -> I2

Halide ion with Silver ion

Ag⁺ + Cl^- -> AgCl_(s) (a white precipitate)

Ag⁺ + Br^- -> AgBr_(s) (a cream precipitate)

Ag⁺ + I^- -> AgI_(s) (a yellow precipitate)

3.3.2 : 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.

	Na2O	MgO	Al2O3	SiO2	P4O10 (or P4O6)	SO3 (or SO2)	Cl2O7
Adding H2O	Na2O + H2O -> 2NaOH	MgO + H2O -> Mg(OH)2	Insoluble	Insoluble	P4O10 + 6H2O -> 4H3PO4	SO3 + H2O -> H2SO4	Cl2O7 + H2O -> HClO4
Adding HCl	Na2O + H+ -> 2Na+ + H2O	MgO + 2H+ -> Mg2+ + H2O	Al2O3 + 6H+ -> 2Al3+ + 3H2O	No reaction	No reaction	No reaction	No reaction
Adding NaOH	No reaction	No reaction	Al2O3 + 2OH- + 3H2O -> 2Al(OH)4	SiO2 + 2OH- -> SiO32- + H2O	P4O10 + 12OH- -> 4PO43- + 6H2O	SO3 + OH- -> SO42- + H2O	Cl2O7 + OH- -> 2ClO4- + H2O
Nature	Basic Oxide	Basic Oxide	Amphoteric Oxide	Acidic Oxide	Acidic Oxide	Acidic Oxide	Acidic Oxide

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.

NaCl : NaCl + H₂O -> Na⁺ + Cl^- + H₂O

MgCl₂ : MgCl₂ -> Mg²⁺ + 2Cl^-

Al₂Cl₆ : Al₂Cl₆ + 6H₂O -> 2Al(OH)₃ + 6HCl

This isn't required....not like it's hard SiCl₄ : SiCl₄ + H₂O -> Si(OH)₄ + 4HCl

PCl₃ : PCl₃ + 3H₂O -> H₃PO₃ + 3HCl

S₂Cl₂ : 2S₂Cl₂ + 2H₂O -> 3S + SO₂ + 4HCl

Cl₂ : Cl₂ + H₂O -> HCl + HClO (Exception : F₂ is such a strong oxidizer : 2F₂ + 2H₂O -> 4HF + O₂)

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