wakaka i know eunice is sitting at my place now hor.
yep thanks to all who told me to get well soon
COS IM GETTING WELL SOON HAHA AND COMING BACK ON MON!

sorry et.. ):
actually should attach eight tables to the back row lor.
then got more life =)
and more fun!

the music's really gone?
YAY!

and eunice comecome let's continue crapping here ^^

comecome.
we shall teach you some chem facts here too to own science lesson!



Common ions and formulae of ionic compounds
Symbols of common ions
You are not expected to know all the names and symbols of common ions, but you should be able to
work out the formulae of ionic compounds. The names and symbols of some ions are shown below.
Positive ions (cations) Negative ions (anions)
Name Symbol Name Symbol
hydrogen H+ chloride Cl–
sodium Na+ bromide Br–
silver Ag+ fluoride F–
potassium K+ iodide I–
lithium Li+ hydrogencarbonate
ammonium hydroxide OH–
barium Ba2+ nitrate
calcium Ca2+ oxide O2–
copper(II) Cu2+ sulphide S2–
magnesium Mg2+ sulphate
zinc Zn2+ carbonate
lead Pb2+
iron(II) Fe2+
iron(III) Fe3+
aluminium Al3+
Formulae of ionic compounds
Ionic compounds contain positive and negative ions. The number of positive charges must equal the
number of negative charges so that the compound has no charge overall. When the positive ion has the
same number of charges as the negative ion, it is easy to work out the formula of the compound formed.
Sodium chloride contains sodium ions, Na+, and chloride ions, Cl–. As both ions have single charges,
the formula is simply written as NaCl, i.e. the positive ion followed by the negative ion with no charges
written. Similarly, ammonium chloride is NH4Cl; magnesium oxide is MgO, and so on. The fun starts
when the number of charges is different, as in magnesium chloride. The “cross-over” method may help:
Step 1 Write the ions side by side:
Step 2 Draw arrows that cross each other:
Step 3 Write the charges at the arrow ends:
Step 4 Write the formula as follows:
a) write the positive ion without its charge:
0J
b) write the number as a subscript unless it is 1:
0J
c) write the negative ion without its charge:
0J&O
d) write the number as a subscript unless it is 1:
0J&O ¼all done!
Watch out for compound ions, e.g. ammonium, hydrogencarbonate, hydroxide, nitrate, sulphate and
carbonate. If you need more than one of them to balance the charges, put brackets around their symbol
at step (a) or (c). For example, sodium hydroxide is NaOH, but magnesium hydroxide is Mg(OH)2;
copper(II) sulphate is CuSO4, but ammonium sulphate is (NH4)2SO4.
NH4
+
HCO3
−
NO3
−
SO24
−
CO2
3
−




AHHHHHHHHHHHHHHHH
FORGET IT.
if u want this sheet here's the link
http://www.creative-chemistry.org.uk/gcse/documents/Module8/N-m08-11.pdf
YES LET'S OWN SCIENCE MAN!
im determined =)
gogo jolly yaada whee zzz tuition centre too!