NAMING COMPOUNDS AND WRITING FORMULAS

1. NAMING BINARY (TWO ELEMENTS) IONIC COMPOUNDS

NaCl

SODIUM CHLORIDE

RULE: THE METAL IS NAMED FIRST LEAVING THE NAME THE SAME. THE NONMETAL IS NAMED SECOND DROPPING OFF THE LAST PART AND ADDING THE SUFFIX IDE.

2. WRITING FORMULAS FOR BINARY COMPOUNDS. THE NUMBER OF ELECTRONS THAT AN ELEMENT GIVES UP OR TAKES ON IS CALLED ITS VALENCE OR OXIDATION NUMBER YOU CAN WRITE A FORMULA FOR A COMPOUND BY JUST CROSSING THE VALENCE NUMBERS DOWN TO THE BOTTOM.

A. WRITE THE FORMULA FOR SODIUM CHLORIDE

Na⁺¹ Cl^-1 EQUALS

NaC1 (THE (1) IS UNDERSTOOD

THIS MEANS THAT SODIUM CHLORIDE IS MADE OF 1 ATOM OF SODIUM AND O ATOM OF CHLORINE.

B. NOTE THAT WHEN ELEMENTS REACT THE ELECTRONS GIVEN UP MUST EQUAL THE ELECTRONS TAKEN ON.

1 ATOM OF Na x 1e^-+ = 1 ATOM OF C! x le^- 1 = 1

C. WRITE THE FORMULA FOR ALUMINUM OXIDE

AL⁺³ O^-2 = AL₂O₃

2 ATOMS OF AL x 3 e = 6 3 ATOMS OF O x 2 e = 6

D. WRITE THE FORMULA FOR CALCIUM OXIDE

Ca⁺² O^-2 = Ca₂O₂

1 ATOM OF Ca x 2 e = ⁺2 1 ATOM OF O x 2 e = ^-2

3. SOME METALS HAVE MORE THAN ONE VALENCE. YOU CAN DETERMINE THIS BY REVERSING THE NUMBER OF ATOMS BACK TO THEIR VALENCE POSITION.

Fe₂ O₃ = Fe⁺³ O^-2

A. SINCE THERE IS MORE THAN ONE TYPE OF IRON THEY MUST BE NAMED DIFFERENTLY. THIS IS DONE BY USING ROMAN NUMERALS AFTER THE NAME OF IRON. THIS WOULD BE NAMED IRON (III) OXIDE.

B. THERE IS ANOTHER SYSTEM FOR HAMING METALS WITH ADDENDUM:

1. WHEN WORKING WITH METALS WITH MORE THAN ONE VALENCE, YOU HAVE TO WORK VALENCE NUMBRS AND THE NUMBER OF ATOMS BACKWARDS TO DETERMINE THE METALS VALENCE. LEAVE THE METAL’S VALENCE EMPTY AND FILL EVERYTHING ELSE AND YOU CAN’T MESS UP.

EXAMPLE: WHAT IS THE VALENCE OF IRON IN Fe₂ O₃ AND WHAT IS THE NAME OF THE COMPOUND?

Fe₂ O₃

A x V + A x V = 0

(2) x (?) + (3) x (-2) = 0

+6 + -6 = 0

IRON VALENCE HAS TO BE +3

THIS MAKES THE NAME OF THIS IRON COMPOUND

IRON (III) OXIDE OR FERRIC OXIDE

2. THERE ARE TWO EXCEPTIONS THAT YOU HAVE TO BE AWARE OF WHEN NAMING THEIR COMPOUNDS.

A. Hg+1 ALWAYS COMBINES IN COMPOUNDS AS Hg2.

B. IN A PEROXIDE OXYGEN ALWAYS COMBINES AS O2 GIVING IT A VALENCE OF -1

IN EACH CASE, WHEN ASKING TO NAME THESE COMPOUNDS, YOU MUST WORK THE VALENCES BACKWARDS. WHEN ASKED TO WRITE THEIR FORMULAS YOU MUST REMEMBER TO ALWAYS COMBINE THEM AS TWO ATOMS.

ADDENDUM TO BINARY COMPOUNDS

1. BINARY COVALENT COMPOUNDS (WHEN TWO NONMETALS REACT, EXAMPLE: PC13). THE RULES ARE THE SAME AS IN BINARY IONIC COMPOUNDS; HOWEVER, SINCE THESE COMPOUNDS HAVE MORE THAN ONE COMBINATION PREFIXES ARE USED TO NUMBER THE ATOMS.

EXAMPLE:

CO = CARBON MONOXIDE

CO₂ = CARBON DIOXIDE

2. THE PREFIXES USED WITH BINARY COVALENT COMPOUNDS ARE AS FOLLOWS:

MONO – 1 HEZA – 6

DI – 2 HEPTA – 7

TRI – 3 OCTA – 8

TETRA – 4 NONA – 9

PENTA – 5 DECA – 1-

BINARY COMPOUNDS THAT GAIN WATER

1. THESE COMPOUNDS ARE CALLED HTDRATES. THEY ARE NAMED AS FOLLOWS:

Cu(SO₄) 5H2O COPPER (II) SULFATE PENTAHYDRATE

THE NAME IS THE SAME WITH THE PROPER PREFIX AND THE WORD HYDRATE.

2. IF A SUBSTANCE IS SAID TO BE IN THE ANHYDROUS FORM IT MEANS THAT IT DOESN’T HAVE THE WATER ATTACHED.

EXAMPLE: Cu(SO4) IS THE ANHYDROUS FORM OF THE SAME COMPOUND.

MORE THAN ONE VALENCE NUMBER. THIS SYSTEM USES THE SUFFIXES “IC” FOR THE HIGH VALENCE AND “OUS” FOR THE LOW VALENCE NUMBER AND LATIN TERMS.

3. THE METALS THAT YOU HAVE TO BE AWARE OF ARE Fe, Hg, Cu, Pb, Ni, Cr, AND Sn.

4. WRITING FORMULAS FOR POLY-ATOMIC MOLECULES.

A. A POLY-ATOMIC ION IS TWO OR MORE ATOMS ACTING AS ONE ATOM. FOR EXAMPLE SO₄^-2. YOU CAN RECOGNIZE THIS FROM AN ELEMENT BECAUSE BOTH LETTERS ARE CAPITALIZED.

B. THESE IONS ARE NAMED BY USING THE NAME OF THE FIRST ELEMENT WITH THE SUFFIX ATE OR ITE.

FOR EXAMPLE:

SO₄^-2 SULFATE

SO₃^-2 SULFITE

THE RULE IS THE POLY-ATOMIC ION WITH THE MOST OXYGEN ENDS IN ATE AND THE ONE WITH THE LEAST OXYGEN ENDS IN ITE. NOTICE THE VALENCES ARE THE SAME FOR BOTH IONS.

MgSO₄ = MAGNESIUM SULFATE

RULE: THE METAL COMES FIRST AND THE NAME STAYS THE SAME. THE POLY-ATOMIC ION ACTING AS A NONMETAL IS AS EXPLAINED BEFORE.

5. WHEN WRITING POLY-ATOMIC MOLECULES IT BECOMES NECESSARY TO USE PARENTHESIS AROUND THE POLY-ATOMIC ION IF THERE IS MORE THAN ONE.

EXAMPLE:

Al₂ (SO₄)₃

6. EXCEPTIONS: OH = HYDROXIDE, NH = AMMONIUM

O = PEROXIDE, HCO = HYDROGENCARBONATE

7. SOME COMPOUNDS ABSORB WATER. SINCE THEIR PROPERTIES ARE DIFFERENT THAN THE ANHYDROUS FORM (WITHOUT WATER) THEY HAVE TO BE NAMED DIFFERENTLY.

EXAMPLE: CuSO = COPPER (II) SULFATE

DuSO₄5H0 = COPPER SULFATE HYDRATE

8. NAMING BINARY ACIDS

RULE: HYDRO FOR THE NYDROGEN AND THE NONMETAL IS NAMED WITH THE SUFFIX “IC”.

EXAMPLE: H₂Cl = HYDROCHLORIC

HB₁ = HYDROBROMIC

9. NAMING TERNARY ACIDS (MORE THAN TWO ELEMENTS)

RULE: USE THE CENTRAL EMEMENT OF THE ANION WITH SUFFIX “IC.”

EXAMPLE: H₂SO₄ = SULFURIC ACID

HNO₃ = NITRIC ACID

WHEN THERE ARE NUMEROUS COMBINATIONS THE FOLLOWING

PATTERN IS FOLLOWED:

HClO₄ = PRE-CHLORIC ACID

HClO₃ = CHLORIC ACID

HClO₂ = CHLORUS ACID

HClO = HYPO – CHLOROUS ACID

H₂SO₄ = SULFURIC

H₂SO₃ = SULFUROUS

NAMING AND FORMULA WRITING SUMMARY

1. A. BINARY IONIC COMPOUNDS

GIVE THE NAME OF NaCl GIVE THE FORMULA FOR

SODIUM CHLORIDE

FOLLOW RULES USE VALENCE NUMBERS

B. METALS WITH MORE THAN ONE VALENCE:

Pb, Sn, Fe, Hg, Cu, Ni, Cr

GIVE THE NAME OF Fe₂O₃ GIVE THE FORMULA FOR

IRON (III) OXIDE OR FERRIC

OXIDE

FOLLOW FULES AND USE NUMERAL FOR VALENCE OF

VALENCE BACKWARDS IRON OR RULE FOR THE

SUFFIX “IC” OR “OUS”

2. BINARY COVALENT

GIVE THE NAME OF N₂O GIVE THE FORMULA FOR

DINITROGEN OXIDE

USE THE SAME RULES WITH DON’T USE VALENCES. THE

PREFIXES PREFIXES TELL YOU THE

NUMBER OF ATOMS

3. POLY-ATOMIC

GIVE THE NAME OF Mg(NO₃)₂ GIVE THE FORMULA FOR

MAGNESIUM NITRATE

USE THE RULES AND CHART USE VALENCE NUMBERS AND

CHART

4. ACIDS

GIVE NAME OF H₂SO₄ WRITE THE FORMULA FOR

SULFURIC ACID

USE THE RULES USE VALENCE NUMBER AS

BEFORE