A - Period 3 Flashcards
What happens to sodium when it reacts? What does it become?
It loses an electron to form the Na+ ion.
What happens to magnesium when it reacts? What does it become?
It loses 2 electrons to become the Mg2+ ion.
Out of sodium and magnesium, which is more reactive and why?
Sodium - it only has to lose one electron, whereas magnesium has to lose 2. It is easier to lose one electron compared to two, therefore sodium is more reactive.
More energy is needed for magnesium to react.
What happens when sodium reacts with cold water?
It reacts vigorously, forming a molten ball on the surface, fizzing and producing hydrogen gas. It also produces sodium hydroxide, creating a strongly alkaline solution (pH 12-14).
What is the equation for the reaction of sodium with cold water?
2Na(s) + 2H2O(l) —> 2NaOH(aq) + H2(g)
What happens when magnesium reacts with cold water?
It reacts very slowly at room temperature and creates a weaker alkaline solution, than that of the reaction between sodium and cold water (pH 9-10). A thin coating of magnesium hydroxide forms on the surface of the metal. Only a few bubbles of hydrogen gas will form after a few days.
What is the equation for the reaction of magnesium with cold water?
Mg(s) + 2H2O(l) —> Mg(OH)2 (aq)+ H2(g)
What happens when magnesium reacts with steam? Give the equation for this reaction.
Magnesium reacts much faster with steam than cold water, as there is more energy. It burns with a white flame.
The reaction forms magnesium oxide and hydrogen.
Mg(s) + H20(g) —> MgO(s) + H2(g)
What do the period 3 elements (except for argon) form when reacted with oxygen?
Are these reactions exothermic or endothermic?
Oxides.
Exothermic.
What happens when sodium reacts with oxygen in the air?
Give the equation for this reaction.
Sodium reacts vigorously and burns brightly in air, with a yellow flame, to form white sodium oxide.
2Na(s) + 1/2O2(g) —> Na2O(s)
What happens when magnesium reacts with oxygen in the air?
Give the equation for this reaction.
A strip of magnesium ribbon reacts vigorously and burns in air with a bright white flame. It produces a white powder (magnesium oxide).
2Mg(s) + O2(g) —> 2MgO(s)
What happens when aluminium reacts with oxygen in the air?
How can this reaction be sped up?
Give the equation for the reaction.
It burns brightly to give aluminium oxide, a white powder.
The reaction is faster if aluminium is powdered.
4Al(s) + 3O2(g) —> 2Al2O3(s)
How does silicon react with oxygen and what is the product?
Give the equation for the reaction.
Silicon reacts slowly so needs to be heated strongly in oxygen to form silicon dioxide.
Si(s) + O2(g) —> SiO2(s)
What are allotropes?
An element with atoms arranged differently.
Red and white phosphorus are ………… of phosphorus.
Fill in the blank.
Allotropes
How do red and white phosphorus react with oxygen respectively?
Give the equation for the reactions.
Red phosphorus must be heated before it will react with oxygen to form phosphorus (V) oxide.
White phosphorus spontaneously combusts in air with a white flame and produced clouds of white smoke.
P4(s) + 5O2(g) —> P4O10(s)
How does sulfur react with oxygen?
Give the equation for the reaction.
Sulfur powder is heated and lowered into a gas jar of oxygen and burns with a blue flame to form the colourless gas sulfur dioxide.
S(s) + O2(g) —> SO2(g)
How is sulfur trioxide formed from sulfur dioxide?
SO2 reacts with oxygen and a vanadium catalyst to form SO3.
Give the formulae of the metal oxides in period 3. (Sodium, magnesium and aluminium oxides)
Na2O
MgO
Al2O3
Why do the period 3 metal oxides have high melting points?
Because they form giant ionic lattices with strong forces of attraction between positive and negative ions which require a large amount of energy to break.
Why does MgO have a higher melting point than Na2O?
Mg forms 2+ ions and forms stronger forces of attraction with negative ions compared to sodium which forms 1+ ions.
Describe the melting point of Al2O3 compared to Na2O and MgO. Why is this the case?
Higher than Na2O but lower than MgO.
The melting point of Al2O3 is lower than expected because the highly charged Al3+ ions distort the oxygen’s electron cloud giving the bonds some covalent character.
How can you predict the covalent character of a bond?
By considering the difference in electronegativities between the two atoms. The larger the difference, the greater the IONIC character of the bond.
Why does silicon dioxide have a higher melting point than the other non-metals in period 3?
It has a giant macro molecular structure where covalent bonding extends throughout the structure. This results in a high melting point as many strong covalent bonds must be broken to melt it.
