Formula writing. IONS. Cation ion – usually metals positive ion (+) loses electrons Anion ion – usually nonmetals negative ion (-) gainies electrons. Ionic Compounds - transfer of electron(s). Ionic compound must be neutral (total + = total -) Write symbol of each ion
Cation ion – usually metals
positive ion (+)
Anion ion – usually nonmetals
negative ion (-)
Ionic compound must be neutral (total + = total -)
If yes, write formula
If no, then criss-cross number (ONLY) of charges (lowest whole number ratio)
Sodium chloride calcium chloride
Na + Cl -
Ca 2+ Cl 1-
Same (1+ = 1-)
2+ = 1-
We do not show 1’s in formulas
Sodium oxide calcium nitrate
Aluminum sulfate iron (III) chloride
You need the () since your ion contains more than one element and you need 2 or more of them to balance the formula
Na 1+ O 2-
Ca 2+ NO31-
Al 3+ SO42-
Fe 3+ Cl 1-
Transition metals will usually have roman numerals. They tell you the CHARGE of the cation
-If no then just name each ion.
-If yes, then name each ion leaving a space after the cation for roman numerals.
See next slide on how to determine the roman numeral
Iron ( ) chloride
Remember the total number of positives must equal the number of negatives. We know the charge of the anion, so do the math.
So what charge must the Fe have to cancel out the 2-’s?
Therefore it is iron (II) chloride. The roman numeral tells us the charge on the iron.
What is the charge for each anion?
How many anions are present?
Total number of negatives
What charge must the cation have to cancel the negatives out?
3+ = 3-
6+ = 6-
Charge of cation
Name of each ionic compound
Contains all nonmetals and use prefixes
Mono- 1 (used sparingly with oxygen)
Di – 2 tri -3 tetra – 4 penta- 5
Hexa – 6 hepta – 7 octa – 8 nona – 9
Nitrogen trichloride diphosphorus tetraoxide
Remember the following
Focus on anion and then add appropriate number of H’s
Binary acid (HX) only 2 elements
Tertiary acid (3 elements)
Hypo- -ite hypo- -ous acid
-ite -ous acid
-ate -ic acid
Per- -ate per- -ic acid
Remember you ate it and it tasted icky
H2SO4 H2CO2 HF
Nitric acid sulfurous acidhydrochloric acid
Sulfate so the –ate becomes -ic
Carbonite so the –ite becomes -ous
Binary so hydro--ic acid
H 1+ NO31-
H 1+ SO32-
H 1+ Cl 1-