3.2.4 - properties of period 3 elements and their oxides

order of elements in p3

Na, Mg, Al, Si, P and S

how does Na react with cold water

what does it produce

eq. for this

• v. exothermic rxn

• melts to form a ball

• fizzes

• moves on surface of water

• sodium hydroxide and hydrogen

2 Na (s) + 2 H2O (l) —→ 2 NaOH (aq) + H2 (g)

observations when Mg reacts with cold water

what does this produce

observations when reacting with steam

what does this produce?

what color is this product solid

eqs. for rxns with steam + cold water

• slow release of bubbles on surface of Mg

• magnesium oxide

• Mg glows bright white

• magnesium oxide

• white

• steam - Mg (s) + H2O (g) —→ MgO (s) + H2 (g)

• cold water - Mg(s) + 2H2O(l) —→ Mg(OH)2(s) + H2(g)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• what do all the elements react with oxygen to form

• oxides

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

what color flame does Na burn with

it produces a w_____solid

eq. for this (learn formula of product)

yellow

white

4 Na (s) + O2 (g)—→ 2 Na2O (s)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• observations when Mg reacts with water - what color light is there?

• what color solid is produced

• eq. for this

• white sparks

• white solid

• 2Mg (s) + O2 (g) —→ 2MgO (s)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• observation when Al reacts with water

• what color solid is produced

• eq. for this

• white SPARKS

• white

• 4Al + 3O2 (g) —→ 2Al2O3 (s)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• observations when Si reacts with water

• what color solid is produced

• eq. for this

• orange sparks

• white solid

• Si + O2 (g) —→ SiO2 (s)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• what color flame does P burn with

• this gives a w______ s______

• eq. for this

• white

• white smoke

• 4P + 5O2 (g) —→ P4O10 (s)

Trends in the reactions of the elements Na, Mg, Al, Si, P and S with oxygen

• what color flame does S burn with

• it forms an a_______ c__________ g__

• eq. for producing SO2

• eq. for producing SO3

• blue

• acidic choking gas

• S + O2 (g) —→ SO2 (g)

• S + 1.5O2 (g) —→ SO3 (g)

what are the ionic metal oxides of period 3

why are they ionic

high or low mp?

why

Na2O, MgO, Al2O3

large EN diff. between metal and O

high

• giant ionic lattices

• lots of ionic bonds —→ electrostatic forces of attraction between oppoisitely charged ions

• these are very strong + take a lot of energy to break

why is there increasing mps from Na to Al

• increased charge on cation (The strength of an ionic bond is directly proportional to the charges on the ions. Na2O contains Na+ ions, MgO contains Mg2+ ions, and Al2O3 contains Al3+ ions. The higher the charge, the stronger the electrostatic attraction to the ion.)

• also, across the period, the metal ions become smaller (Na+ > Mg2+ > Al3+). Smaller ions can get closer together, resulting in stronger attractions (greater lattice enthalpy of dissociation), making it harder to separate the ions during melting.

• so stronger ionic bonds

why is the melting point of Al2O3 is sometimes lower than that of MgO

the high-charge Al3+ ion distorts the O2- electron cloud, giving it significant covalent character.

what is the macromolecular metal oxide in period 3

is its mp low or high

why

SiO2

very high

has many strong covalent bonds between atoms.

High energy needed to break these

what are the simple molecular metal oxides in period 3

lower or higher mps

why

why are they covalent

why does P4O10 have a higher mp than SO2

P4O10 and SO2

lower

weak intermolecular forces between molecules (van der waals + permanent dipoles)

small electronegativity difference between the non-metal and O atoms

it is a bigger molecule, so more e-s, so more vdWs, so higher mp

how to prove experimentally all these compounds contain ions

melt the solids and show they conduct electricity

The reactions of the oxides of the elements Na —→ S with water (check sheet from booklet)

• what do metal ionic oxides react with water to form

• are these acidic or alklaine

• reaction of Na2O

• what pH is the solution formed

• hydroxides

• alkaline

• Na2O (s) + H2O (l) —→ 2Na+ (aq) + 2OH- (aq)

• 13

are ionic oxides basic or acidic?

summary of rxns of period 3 oxides

summary of reactions of period 3 oxides with water