Formula writing

IONS

Cation ion – usually metalspositive ion (+)loses electrons

Anion ion – usually nonmetalsnegative ion (-)gainies electrons

Ionic Compounds- transfer of electron(s)

Ionic compound must be neutral (total + = total -)1. Write symbol of each ion2. See if the charges balance outIf yes, write formulaIf no, then criss-cross number (ONLY) of charges (lowest whole

number ratio)Sodium chloride calcium chloride

Na + Cl -

Same (1+ = 1-)

NaCl

Ca 2+ Cl 1-

2+ = 1-

CaCl2

We do not show 1’s in formulas

More examples

Sodium oxide calcium nitrate

Aluminum sulfate iron (III) chloride

Na 1+ O 2-

Na2O

Ca 2+ NO3 1-

Ca(NO3)2

You need the () since your ion contains more than one element and you need 2 or more of them to balance the formula

Al 3+ SO4 2-

Al2(SO4)3

Fe 3+ Cl 1-

FeCl3

Transition metals will usually have roman numerals. They tell you the CHARGE of the cation

Nomenclature of ionics(naming)

1) Id the cation.2) Ask if it is a transition metal, Sn, or Pb?

-If no then just name each ion.-If yes, then name each ion leaving a space after the cation for roman numerals.

CaCl2 FeCl2

Calcium chloride Iron ( ) chloride

See next slide on how to determine the roman numeral

How to figure out the charge of the cation?

Remember the total number of positives must equal the number of negatives. We know the charge of the anion, so do the math.

FeCl2

Cl 1-

Cl 1-Fe

So what charge must the Fe have to cancel out the 2-’s?2+

Therefore it is iron (II) chloride. The roman numeral tells us the charge on the iron.

Let’s try some more.

Co(NO3)3 Ni2(SO4)3

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?

Charge of cation

Name of each ionic compound

1- 2-

3 3

(1-)(3) =3- (2-)(3)=6-

3+ = 3- 6+ = 6-

3+ (6+)/2= 3+

Cobalt(III) nitrateNickel(III) sulfate

Molecular compounds

Contains all nonmetals and use prefixesMono- 1 (used sparingly with oxygen)Di – 2 tri -3 tetra – 4 penta- 5Hexa – 6 hepta – 7 octa – 8 nona – 9Deca- 10Nitrogen trichloride diphosphorus tetraoxide

NCl3P2O4

Acids – Contain H’s listed first

Remember the followingFocus on anion and then add appropriate number of H’sBinary acid (HX) only 2 elementsHydro- -ic acid

Tertiary acid (3 elements)Hypo- -ite hypo- -ous acid -ite -ous acid -ate -ic acidPer- -ate per- -ic acid

Remember you ate it and it tasted icky

Naming and formula writing for acids

H2SO4 H2CO2 HF

Nitric acid sulfurous acid hydrochloric acid

H 1+ NO3 1-

HNO3

H 1+ SO3 2-

H2SO3

H 1+ Cl 1-

HCl

Sulfate so the –ate becomes -ic

Sulfuric acid

Carbonite so the –ite becomes -ous

Carbonous acid

Binary so hydro- -ic acid

Hydrofluoric acid

nitrate

sulfite