2.4- Period 3 Flashcards
Explain the reactions of sodium and magnesium with cold water
Sodium reacts with cold water, if fizzes around on the surface
Magnesium reacts very slowly with cold water to form the hydroxide but reacts more readily with steam to form the oxide
Give the trends in the reaction of the period 3 elemets with oxygen
Sodium burns with a yellow flame to produce a white solid
Mg,AL,Si,P all burn with a white flame to give a white solid smoke
S burns with a blue flame to form an acidic choking gas
Where is sodium stored in
Sodium is stored under oil and phosphorous under water to stop these elements coming into contact and reacting with the air
What are the properties of the ionic oxides
.The metal oxides are ionic, they have high melting points
. Ionic giant lattice structure, stronger forces of attrction between oppositely charged ions, higher mp
. Increaed charge makes ionic forces stronger so going from Na to Al leads to increasing melting points
Why is there covalent character in Al2O3
. Explained by the electronegativity difference being lsmaller between the aluminium ion and the oxygen ion
. High charge being able to get clsoe to the oxide ion and distorting the oxide charge cloud
What are the properties of the macromolecular oxides
SiO2 is macromolecular, has many very strong covalent bonds between atoms, high energy neede to break the many strong covalent bonds very high mp and bp
What are the properties of the simple molecular oxides, explain using P4O10 and SO2 ,and the difference in their melting and boiling points
. Examples include P4O10 and SO2
. There are weak intermolecular forces between the molecules, there are van der waals and permanent dipoles
. So have lower mps
.Covalent because of the small electronegativity difference between the non metal and O atoms
. As P4O10 is a molecule that is bigger with more electrons, it will have more electrons than SO2 and will have larger van der waals hence a higher melting point
How do the metal ionic oxides react with water
. Metal ionic oxides tend to react with water to form hydroxides that are alkaline
. The ionic oxides are basic because the oxide ions accept protons to become hydroxides ions in this reaction
. The pH of the reactions dereases with the greater charge becasue it is less likely to dissociate
Na- ph 13
Mg- pH 9
Why do Al2 and SiO2 not dissolve in water
.Because the high strength of the Al2O3 ionic lattice and the SiO2 macromolecular structure so they give the neutral pH 7
Give uses of MgO
MgO is used for treating acid in rivers and the stomach as it is sparingly soluble and weakly alakaline
How do the simple molecular oxides react with water
The simples molecular oxides react with water to give acids
P4O10 would make phosphoric acid
SO2 would make H2SO3
SO3 woudl make H2SO4
What are the trends of the period 3 oxides reactions with water
Ionic metal oxides show basic behaviour
Non metal covalent oxides show acidic behaviour
Aluminium oxide is amphoteric
What do the basic oxides react with acids to make
The basic oxidces react with acids to make salts and water
How does aluminium oxide react with acids and bases
.Aluminium oxide forms a salt and water when reacting with an acid
.When aluminium oxide reacts as an acid, this is the equation
Al2O3 + 2NaOH + 3H2O > 2NaAl(OH)4
How does SiO2 react with alkalis
.Because of the giant covalent structure it cannot dissolve or react with an alkali , it can react with very concentrated NaOH however
