13.1 Reactions of Period 3 Elements - TE.ppt

this lecture is about period 3 elements, about properties and periodicity

1. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
OBJECTIVES:
To describe the reaction of Na and Mg with water
To describe the trend in reactions of period 3 elements
with oxygen
WITHOUT LOOKING…
At a periodic table can you:
Name the elements in period 3?
KEY WORDS:
REDOX
ALLOTROPE
FLAME TEST
OXIDATION STATE

2. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
GROUP 3

3. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
FROM AS…
What can you remember about the following for period 3
elements?
Atomic Radius –
Melting/Boiling Point –

4. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
Atomic Radius
– Decreases across period
- Extra protons pull electrons closer
- No extra shielding
Melting/Boiling Point
- Increase up to silicon then decrease
- Metallic bonding in Na, Mg and Al
- Macromolecular tetrahedral structure in Si
- P, S, Cl are all molecular – M.P & B.P depend on VdW
- Ar exists as individual atoms
First Ionisation Energy -

5. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
INVESTIGATING REACTIONS WITH WATER &
OXYGEN
Complete the practical on the sheet and try to fill out the
table
Try and answer the questions on the sheet

6. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
REACTIONS WITH WATER
Sodium:
Reacts vigorously forming a molten ball on the surface,
fizzing and producing H
2 gas
2Na
(s)
+ 2H
2
O
(l)
 2NaOH
(aq)
+ H
2(g)
Magnesium:
Reacts slowly with no visible reaction
It forms a weakly alkaline solution  how we know it
reacts
Mg
(s)
+ 2H
2
O
(l)
 Mg(OH)
2(aq)
+ H
2(g)

7. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
WHY DOES SODIUM REACT MORE?
When they react:
• Na loses 1 electron
• Mg loses 2 electrons
It takes less energy to remove 1 electron than it does 2
More energy (usually heat) is needed for Mg to react
Mg(OH)
2
is not very soluble in water, so produces relatively
few OH
-
ions. This makes it a weaker alkali than NaOH

8. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
REACTIONS WITH OXYGEN
ElementOxideOxidation
State of
Element
Extent of Reaction Flame
Na Na
2O +1 Vigorous Yellow
Mg MgO +2 Vigorous Brilliant
White
Al Al
2
O
3
+3 Slow N/A
Si SiO
2
+4 Slow N/A
P P
4O
10 +5 One allotrope
*

spontaneously combusts;
the other requires
heating
Brilliant
White
S SO
2
+4 Burns steadily Blue
*Allotrope: same element but atoms arranged differently

9. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
REACTIONS WITH OXYGEN
2Na
(s)
+ ½O
2(g)
 Na
2
O
(s)
Mg
(s) + ½O
2(g)  MgO
(s)
2Al
(s)
+ 1½O
2(g)
 Al
2
O
3(s)
Si
(s) + O
2(g)  SiO
2(s)
P
4(s)
+ 5O
2(g)
 P
4
O
10(s)
S
(s)
+ O
2(g)
 SO
2(g)
0 0 +1 -2
0 0 +2 -2
0 0 +3 -2
0 0 +4 -2
0 0 +5 -2
0 0 +4 -2
All elements form oxides
when they react with
oxygen
They’re usually in their
highest oxidation states –
the same as their group
number
Only exception is sulpur –
it forms SO
2
giving it a +4
oxidation state. High
temperature and catalyst
is required to form SO
3
.

10. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
SUMMARY TEST – Notes away!
1a) Identify elements A, B and C
1b) Write an equation
for each of these
reactions
2a) Write equations for the reaction of i) Sodium and ii)
Magnesium with water
2b) Write an equation to show the reaction of i) Aluminium
and ii) Silicon with oxygen
ElementReaction in airFlame
A Vigorous Yellow
B Vigorous Brilliant
White
C Burns steadilyBlue

11. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
SUMMARY TEST – Notes away!
1a) A = Sodium; B = Magnesium; C = Sulphur
1b)
2Na
(s) + ½O
2(g)  Na
2O
(s)
Mg
(s)
+ ½O
2(g)
 MgO
(s)
S
(s)
+ O
2(g)
 SO
2(g)

12. 13.1 REACTIONS OF PERIOD 3 ELEMENTS
SUMMARY TEST – Notes away!
2a)
2Na
(s) + 2H
2O
(l)  2NaOH
(aq) + H
2(g)
Mg
(s) + 2H
2O
(l)  Mg(OH)
2(aq) + H
2(g)
2b)
2Al
(s)
+ 1½O
2(g)
 Al
2
O
3(s)
S
(s)
+ O
2(g)
 SO
2(g)

13. How low can you go?? Write what you can do and what
grade this is  show some proof you can do this!
I CAN… I AM…
Describe the reactions of period 3 elements with
water and oxygen
C
Explain why sodium reacts more vigorously than
magnesium
B
Calculate the oxidation states in the reactionsA
Provide balanced equations for reactions of
period 3 elements with oxygen
A*
4.1 NAMING ORGANIC COMPOUNDS