Periodicity 2 notes

chapter 22.1

Physical properties of period 3 elements

• Silicon is a metalloid that can conduct electricity to a certain extent

• P,S and Cl are non metals that cannot conduct electricity

• Ar is a inert/chemically unreactive noble gas

oxidation state of elements

Na:1+

Mg:2+

Al:3+

Si:4+

P: 3-

S:2-

Cl: 1-

Ar: has no oxidation state

Reactions of sodium and water

2Na(s) + 2H2O(1) 2NaOH(aq) + H2(g)

speed: vigorous

PH:14

Reaction of magnesium and water

Mg(s) + 2H₂O(l)→ Mg(OH)2(aq) + H2(g)

Reaction of magnesium and steam

Mg(s) + H2O(g) MgO(s) + H2(g)

sodium and oxygen symbol equation

2Na(s) + 1/2O(g) → Na₂O(s)

Magnesium and oxygen symbol equation

2Mg(s) + 02(g) → 2MgO(s)

Aluminium and oxygen symbol equation

4Al(s) + 302(g) → 2Al203(s)

formation of silicon dioxide symbol equation

Si(s) + O2(g) → SiO2(s)

phosphorus and oxygen symbol equation

4P(s) + 502(g) P4O10(s)

If there is a lack of oxygen, phosphorus trioxide is formed

Physical properties of the metals in period 3

shiny, conduct electricity, and react with acids to give hydrogen. They are malleable (able to be beaten into sheets) and ductile (able to be drawn into wires). They are good conductors of heat.

Properties of the period 3 non-metals:

They tend to be brittle - they are poor conductors of heat.

in peroxides the oxidation state of oxygen is 1- but in other compounds it’s always 2-

chapter 22.2

type of bonding in aluminium oxide: aluminium is ionic with covalent character because it is a small ion that can distort the electron cloud.

metal oxides (Na2O, MgO and Al2O3) have giant ionic lattices and high melting and boiling points

to predict whether it has ionic character or not, consider the difference in electronegativities

non-metal oxides

silicon dioxide

structure: macromolecular/ giant covalent

MP: High with strong covalent bonds that require lots of energy to break

phosphorous oxide(P4O10)

structure: macromolecular

IMF: van der Waals and permanent dipole-dipole forces

MP: Low

states at room temperature, 298 K, sulfur dioxide and sulfur trioxide

PO10 > SO3 > SO₂

Why do the melting points get weaker across the period?

There is an increase in intermolecular van der Waals forces between larger molecules

structures of oxo acids:

phosphoric acid:

P: has 5 electrons

shape of all 3 oxo ions: a perfect tetrahedron that has delocalisation

sulfuric acid

number of electrons: 6

bond angle of an ideal tetrahedron: 109.5

lengths of bonds in the phosphorus oxo anion: they are all the same length

number of electrons in phosphorus’ outer main shell: 5

Number of electrons in sulfur’s outer main shell: 10 electrons

number of electrons sulfur has in its outer main shell in the sulfate (IV) anion: 10

Na₂O(s) + H2O(l) →2Na+ (aq) + 2OH-(aq) pH of solution~14

MgO(s) + H₂O(1) →Mg(OH)2(s)Mg2+(aq) + 2OH-(aq) 10-13

Which metal oxides are insoluble: aluminium oxide and silicon oxide

acidic oxides:

PO(s) + 6H2O(l) →4H3PO4 (aq)

H3PO4(aq)→ H+ (aq) + H2PO(aq)(reversible reaction)

SO2(g) + H₂O(l) →H2SO3(aq)partially dissociates in water

H₂SO3(aq)H+(aq) + HSO3 (aq)

SO3(g) + H2O(l) H2SO(aq) H+(aq) + HSO(aq) violient reaction

Key points of the behaviour of oxides:

Na and Mg are ions

Na2O is a strong base that dissolves to form an alkaline solution

MgO is less soluble and is a weaker base

Aluminium oxide cannot be separated

General trend: Solutions of the oxides of the elements go from alkaline to acidic across the period.

reactions with acids:

Na2O (s) + H2SO4 (aq) → Na2 SO (aq) + H2O(l)

MgO(s) + 2HCl(aq) → MgCl2(aq) + H₂O(l)

Al₂O3(s) + 6HCl(aq) → 2AICl3 (aq) + 3H₂O(l)

Al₂O3(s) + 2NaOH(aq) + 3H2O(l)→ 2NaAl(OH))aq)

Properties of silicon dioxide: weak acid

SiO₂(s) + 2NaOH(aq)→ Na₂SiO3(aq) + H₂O(l)

Si02[s) + Ca0(I) →CaSi03 (l)

phosphorous pentoxide

H3PO4(aq) + NaOH(aq)→ NaH2PO4(aq) + H₂0(l)

NaH PO (aq) + NaOH(aq)→ Na2HPO4(aq) + H₂O(l)

Na2HPO4 (aq) + NaOH(aq)→ Na3PO4(aq) + H₂O(l)

Overall equation:

3NaOH(aq) + H3PO4(aq)Na3PO4(aq) + 3H2O(l)

SO2(aq) + NaOH(aq) → NaHSO3 (aq)

Ca0(s) + SO2(g]→ CaS03(s)

metal chlorides

NaCl and MgCl2

Aluminium chloride structure:

The aluminium has only six electrons in its outer main shell, and it forms a dimer in which coordinate covalent bonds form between lone pairs of electrons on the chlorine atoms and the electron-deficient aluminium atoms.

Silicon tetrachloride:

holds 18 electrons in the outer main shell, SiCl4

structure: gaint ionic lattice

aluminium chloride in water

AlCl3 (s) +3H2O (1) → Al(OH)3(s) + 3H+(aq) + 3Cl-(aq)

[Al(H₂O)] 3+(aq) →[Al(H₂O) (OH)] 2+(aq) + H+(aq)

SiCl(l) + 2H2O(l)→ SiO2(s) + 4H+(aq) + 4Cl-(aq)

PCI5(s) + 4H2O(1)→H,PO(aq) + 5H+(aq) + 5Cl-(aq)