Period Three Flashcards
What is the trend for atomic radius accross period three?
Atomic radius decrease accross period three, there are more protons yet similar shells and shielding. So the attraction between the nucleus and outer electrons is stronger
What is the trend for forst ionisation energy accross period three?
First ionisation energy increases, more protons but similar shells and shielding sonthe attractuon between the nucleus and electron being lost is stronger
What happens when sodium reacts with water?
It fizzes ciolently, melts imto a ball and dissolves
What halpens when magnesium reacts with cold water?
Very slow reaction, bubbles form
What happens when magneisum reacts with steam?
Bright white light ,a white solid powder of magnesium oxide
What elements from period three do not react with water?
Aluminium, silicon, sulfur and argon
Why does aluminium not react with water?
It is coated in AlO3
What happens when chlorine reacts with water? What type of reaction is this?
A pale green colution forms, and it turns litmus paper red and then white
Its a disproportionate reaction, because chlorine is oxidised to HClO and reduced to HCl
What is a disproportionate reaction?
Where an element is blth oxidised and reduced
What can be seen when sodium, magnesium and aluminium reacts with oxygen?
Sodium- yellow flame, white solid of NaO2 forms
Magnesium- bright white light, white powder of MgO forms
Aluminium - slow reaction, a white solid of Al2O3 dorms
What happens when silicon reacts with oxygen?
Very slow reaction to form SiO2
What are the two different reactions of phosphorus and oxygen? What different observations can be seen?
P4 + 5O2 —> P4O10 (white flames)
4P + 5O2 —> P4O10 (white fumes)
What happens when sulfur reacts with oxygen?
Blue flame, produces SO2 (choking gas)
What happens when sulfur dioxide continues to react with oxugen?
SO3 is formed
Between metal oxides and non-metal oxides, whoch is acidic and which is basic?
Metal oxides are basic, non-metal oxides are acidoc
How do metal oxides react with water?
They react with water to produce metal hydroxides. As the oxide ions react with water to form hydroxide ions.
Describe the solubility and pH of metal hydroxides
pH decreases accross the period
Solubility decreases, NaOH is very soluble, Mg(OH)2 is sparingly soluble, and aluminium oxide does not react to form a hydroxide so is insoluble.
Hpw do non-metal oxides react with water?
They react woth water to produce solutions containing H+ ions, with low pH
What happens when silicon oxide reacts woth water?
It is insoluble
What is the product and pH when phosphorus oxide reacts with water?
It produces H3PO4, pH 1
What is the product and pH when SO3 reacts woth water?
Produces H2SO4, pH 1
What is the product and pH when SO2 reacts with water? What reaction forms?
Produces H2SO3, pH 3
Forms a reversible reaction, where equilibrium lies to the left
Are period three ionic oxides basic or acidic?
Basic
Are period three covalent oxides basic or acidic?
Acidic
What does amphoteric mean?
A species that can act as an acid or a base.
Give an example lf an amphoteric oxide
Aluminium oxide
Give examples lf reactions that show aluminium oxode is amphoteric
Reactions with acids
• Al2O3 + 6HNO3 —> 2Al(NO3) + 3H2O
• Al2O3 + 3H2SO4 —> Al2(SO4)3 + 3H2O
Reaction with bases
• Al2O3 + 2NaOH +H2O —> NaAl(OH)4
What happens when aluminium salts are dissolved in water?
An acidic solution is formed.
The lattice breaks down and the aluminium ions become surrounded by six water molecules.
Each molecule bonded with co-ordinate bonds. This forms a hexaaqua ion.
The charge in the Al ions causes the electron density in the water molecules to move closer to the Al ion. So the water molecules become polarised.
This breaks an O-H bond in one of the water molecules, whoch donates a H+ ion.
This creates a reversible reaction
What happens when a strong base is added to a hexaaqua ion?
Produces an insoluble precipitate of aluminium hydroxide Al(H2O)3(OH)3 and water.
Name an amphoteric hydroxide
Aluminium hydroxide
Aluminium hydroxide is amphoteric, when does it act as an acid? Give equations and observations
When reacted with a base, and excess sodium hydroxide is used
Al(H2O)3(OH)3 + OH- —> [Al(H2O)2(OH)4 ]- + H2O
The white precipitate of aluminium hydroxide dissolves to form a colourless soultion
Aluminium hydroxide is amphoteric, when does it act as a base? Give equations and observations
Acts as a base when reacted with an acid
Al(H2O)3(OH)3 + 3H+ —> [Al(H2O)6 ]3+
The white precipitate lf aluminium hydroxide dissolves to form a colourless solution.
