A-LEVEL CHEMISTRY: 3.2.4: Periodicity of Period 3 (SaveMyExams) Flashcards
Magnesium reacts very ___ with cold water to form the ___, but reacts more ___ with ___ to form the ___.
slowly, hydroxide, quickly, steam, oxide
all Period 3 Elements react with oxygen to form…
oxides
Sodium burns with a ___ flame when it reacts with Oxygen to produce a ___ solid.
yellow, white
explain the reaction between Sodium and Oxygen: (2)
-Na burns with yellow flame
-produces white solid
explain the reaction between Magnesium and Oxygen: (2)
-Mg burns with white flame
-produces white solid & smoke
explain the reaction between Aluminium and Oxygen: (2)
-Al burns with white flame
-produces white solid & smoke
explain the reaction between Silicon and Oxygen: (2)
-Si burns with white flame
-produces white solid & smoke
explain the reaction between Sulfur and Oxygen: (2)
-S burns with blue flame
-produces acidic choking gas
equation for reaction between Sodium & Oxygen:
4Na (s) + O2 (g) —–> 2Na2O (s)
equation for reaction between Magnesium & Oxygen:
2Mg (s) + O2 —–> 2MgO (s)
equation for reaction between Aluminium & Oxygen:
4Al (s) + 3O2 (g) —–> 2Al2O3 (s)
equation for reaction between Silicon & Oxygen:
Si (s) + O2 (g) —–> SiO2 (s)
equation for reaction between Phosphorus & Oxygen:
4P (s) + 5O2 (g) —–> P4O10 (s)
equation for reaction between Sulfur & Oxygen:
S (s) + O2 (g) —–> SO2 (g)
explain the reaction between Phosphorus and Oxygen: (2)
-P burns with white flame
-produces white solid & smoke
Sodium is stored in ___, & Phosphorus is stored in ___. why?
paraffin oil, water
to prevent them from reacting with Oxygen
the Metal Oxides (Na2O, MgO, Al2O3) are ___.
Ionic
explain why Ionic Metal Oxides have ___ Melting Points: (3)
High
-Giant ionic lattice structures
-strong electrostatic forces of attraction between between +ve & -ve ions
why are Metal Oxides ionic?
due to high electronegativity difference between +ve Metal ions & -ve oxygen ions
explain the trend in the MPs of Ionic Oxides across Period 3:
-increases
-increasing atomic number
-increasing nuclear charge
-increased charge on the cation
-stronger electrostatic forces of attraction
how to prove that compounds contain ions:
Melt the solids & test of they Conduct electricity
SiO2 is ___.
macromolecular
SiO2 is ___. explain the mp & bp:
Macromolecular
v. high mp & bp because:
-many v. strong covalent bonds between atoms
-high energy needed to break the many strong covalent bonds
-∴ v. high mp & bp
P4O10 (s) and SO2 (g) are ___ ___. explain their properties. (3)
simple molecular
-weak intermolecular forces (van der waals + permanent dipoles)
-low mp’s
-covalent because of small electronegativity difference between Non-Metal & O atoms
Metal ionic oxides tend to react with water to form ___ which are ___.
hydroxides, alkaline
Na2O (s) + H2O (l) —–> …
2Na+ (aq) + 2OH- (aq)
pH 13
(this is a vigorous exothermic reaction)
Al2O3 and SiO2 ___ ___ ___ in water. why?
do not dissolve
because of the high strength of the Al2O3 ionic lattice & the SiO2 macromolecular structure, so they give a neutral pH 7
MgO is better than NaOH for treating acid in rivers & stomach. why?
because it is only sparingly soluble & weakly alkaline, so using an excess would not make the water excessively alkaline
The non-metal, simple molecular, covalent, oxides react with water to give…
acids
vigorous exothermic reaction between P4O10 & H2O:
pH:
P4O10 (s) + 6 H2O (l) —–> 4 H3PO4
(aq)
pH: 0
the trend when oxides react with water is that ionic metal oxides show ___ behaviour, whereas the non-metal covalent oxides show ___ behaviour.
basic, acidic
ionic metal oxides react with acids to make salts:
acid + base —–> salt + water
Amphoteric oxides:
Aluminium oxide can act as both an acid and an alkali and is therefore called amphoteric
SiO2 has a ___ ___ ___ with ___ ___ ___. what does this stop?
giant covalent structure, very strong bonds
this stop SiO2 dissolving or reacting with water and weak alkali solutions.
it will, however, react with very concentrated NaOH
what will SiO2 still react with?
very concentrated NaOH
why doesn’t SiO2 dissolve or react with water or weak alkali solutions? (2)
because:
-giant covalent structure
-very strong bonds
