copyright sautter 2003 chemical formulae* how to write formulas from names and names from formulas*...
TRANSCRIPT
Copyright Sautter 2003
CHEMICAL FORMULAE*
HOW TO WRITE FORMULAS FROM NAMES AND NAMES
FROM FORMULAS*
* SOME BOOKS USE FORMULAE ENDING IN AE WHICH IS THE LATIN PLURAL INSTEAD OF FORMULAS
TYPE OF COMPOUNDS
• (1) IONIC COMPOUNDS – THOSE CONSISTING PRIMARILY OF METALS COMBINED WITH NONMETALS
• (A METAL COMBINED WITH A NONMETAL IS CALLED A SALT. SODIUM CHLORIDE OR “TABLE SALT” IS NOT THE ONLY SALT, THERE ARE MANY DIFFERENT KINDS OF SALTS. IT HOWEVER IS ONE OF THE MOST COMMON SALTS.)
• (2) MOLECULAR COMPOUNDS – THOSE CONSISTING OF NONMETALS
WHAT ARE IONS?CHARGED ATOMS OR GROUPS OF ATOMS
THERE ARE TWO KINDS OF IONS, POSITIVE AND NEGATIVE
• POSITIVE IONS ARE ATOMS OR GROUPS OF ATOMS WITH MISSING ELECTRONS
• THESE IONS USUALLY CONSIST OF METALS
• THEY ARE ALSO CALLED CATIONS
• NEGATIVE ION ARE ATOMS OR GROUPS OF ATOMS WITH EXTRA ELECTRONS
• THESE IONS USUALLY CONSIST OF NONMETALS
• THEY ARE ALSO CALLED ANIONS (NOT DOG IONS AS YOU MIGHT EXPECT !!)
SOME COMMON CATIONS (POSITIVE IONS)
• NAME• SODIUM
• ZINC
• POTASSIUM
• CALCIUM
• MAGNESIUM
• COPPER II (CUPRIC)
• IRON II (FERROUS)
• IRON III (FERRIC)• AMMONIUM*
*ONE OF THE FEW POLYATOMIC CATIONS
• FORMULAS• Na+1
• Zn+2
• K+1
• Ca+2
• Mg+2
• Cu+2
• Fe+2
• Fe+3
• NH4+1
SOME COMMON ANIONS (NEGATIVE IONS)
• NAMES• CHLORIDE
• SULFIDE
• BROMIDE
• SULFATE
• SULFITE
• NITRATE
• NITRITE
• CARBONATE
• CHROMATE
• FORMULAS• Cl-1
• S-2
• Br-1
• SO4-2
• SO3-2
• NO3-1
• NO2-1
• CO3-2
• CrO4-2
SOME RULES REGARDING CATIONS (POSITIVE IONS)
• IONS FROM COLUMN I (ALKALI METALS) ON THE PERIODIC TABLE ARE ALWAYS +1
• IONS FROM COLUMN II (ALKALINE EARTH METALS) ON THE PERIODIC TABLE ARE ALWAYS +2
• IONS FROM COLUMN II (THE ALUMINIUM GROUP) ON THE PERIODIC TABLE ARE +3
• THE TRANSITIONAL METALS HAVE VARIABLE CHARGES RANGING FROM +1 TO +5
• EXAMPLES:
• COLUMN I COLUMN II
• Na+1 Ca+2
• K+1 Mg+2
• etc. etc.
• COLUMN III
• Al+3
• Ga+3
• TRANSITIONAL METALS
• Cu+2
• Fe+2
• Cr+3
TRANSITIONAL METALS WITH VARIABLE CHARGE STATES
• SOME TRANSITIONAL METALS CAN EXSIST AS IONS IN TWO DIFFERENT CHARGE STATES. SOME OF THESE ELEMENTS ARE COPPER, TIN, IRON, COBALT, LEAD, MERCURY, CHROMIUM AND MANGANESE.
• * THESE VARIABLE CHARGES HAVE NO PATTERN AND MUST BE MEMORIZED
• EXAMPLES:• COPPER +1 OR +2• TIN +2 OR +4• IRON +2 OR +3• COBALT +2 OR +3• LEAD +2 OR +4• MERCURY +1 OR +2• CHROMIUM +2 OR +3• MANGANESE +2 OR +3• * THE SAME ATOM WITH
DIFFERENT CHARGE STATES ARE DESIGNATED USING ROMAN NUMERIALS SUCH AS COPPER I FOR Cu+1 OR LEAD II FOR Pb+2
RULES REGARDING FORMULAS AND NAMES FOR ANIONS (NEGATIVE IONS)
• ANIONS FROM COLUMN VII (HALOGENS) ARE CHARGED –1
• ANIONS FROM COLUMN VI (OXYGEN GROUP) ARE CHARGED –2
• ANIONS FROM COLUMN V (NITROGEN GROUP) ARE CHARGED –3 WHEN THE IONS ARE SINGLE ATOMS (MONATOMIC)
• EXAMPLES:
• COLUMN VII
• Cl-1
• Br-1
• COLUMN VI
• S-2
• O-2
• COLUMN V
• N-3
P-3
NAMING MONATOMIC (SINGLE ATOM) ANIONS
• ANIONS THAT CONSIST OF ONLY ONE ATOM END IN ALWAYS “IDE”.
• ANIONS THAT CONSIST OF MORE THAN ONE ATOM BUT CONTAIN NO OXYGEN ALSO END IN “IDE”
• THE HYROXIDE ION IS AN EXCEPTION IN THAT IT CONTAINS OXYGEN AND POLYATOMIC BUT ENDS IN “IDE”
• CHLORIDE Cl-1
• SULFIDE S-2
• NITRIDE N-3
• CYANIDE CN-1
• THIOCYANIDE SCN-1
• HYDROXIDE OH-1
POLYATOMIC IONS ARE THOSE THAT CONSIST OF MORE THAN ONE ATOM. MOST ARE ANIONS.
• POLYATOMIC IONS THAT CONTAIN OXYGEN END IN “ATE” OR “ITE”
• ONCE POLYATOMIC IONS ENDING IN “ATE” ARE KNOWN, IONS OF SIMILAR COMPOSITION BUT DIFFERING BY ONE LESS OXYGEN ATOM END IN “ITE”
• EXAMPLES:• SULFATE • SO4
-2
• SULFITE HAS ONE LESS OXYGEN ATOM
• SO3-2
• NITRATE• NO3
-1
• NITRITE HAS ONE LESS OXYGEN ATOM
• NO2-1
POLYATOMIC IONS ARE THOSE THAT CONSIST OF MORE THAN ONE ATOM. MOST ARE ANIONS.
• Polyatomic anions which contain one more oxygen than the “ate” form are given the prefix “per”
• ClO3-1 is chlorate, ClO4
-1 is perchlorate
• Polyatomic anions which contain one less oxygen than the “ite” form are given the prefix “hypo”
• ClO2-1 is chlorite, ClO-1 is hypochlorite
FORMULAS OF IONIC COMPOUNDS(CATIONS ARE ALWAYS NAMED FIRST FOLLOWED BY THE
NAME OF THE ANION IN THE COMPOUND)
• IONIC SALTS ARE FORMED WHEN CATIONS COMBINE WITH ANIONS
• THE NET CHARGE ON ALL SALTS MUST BE ZERO WHICH MEANS ALL THE POSITIVE CHARGES ON THE CATIONS MUST BALANCE ALL THE NEGATIVE CHARGE ON THE ANIONS
• EXAMPLE:
• WHEN SODIUM CHLORIDE IS FORMED FROM A POSITIVE SODIUM ION AND A NEGATIVE CHLORIDE ION, JUST ONE SODIUM WITH A +1 CHARGE IS REQUIRED TO BALANCE JUST ONE CHLORIDE WITH A –1 CHARGE. SO THE FORMULA IS JUST NaCl.
WHAT ABOUT FORMULAS FOR COMPOUNDS WHEN THE POSITIVE AND NEGATIVE CHARGES DON’T
EXACTLY BALANCE
• ZINC CHLORIDE CONSISTS OF ZINC WITH A +2 CHARGE AND CHLORIDE WITH A –1 CHARGE.
• IN ORDER TO BALANCE THE CHARGES, ONE ZINC MUST COMBINE WITH TWO CHLORIDES. THE FORMULA FOR ZINC CHLORIDE IS ZnCl2.
• (+2) + ( 2 x (-1)) = 0
• IRON III SULFIDE CONSISTS OF TWO IRON ATOMS AND THREE SULFUR ATOMS.
• EACH IRON III ION HAS A +3 CHARGE AND EACH SULFIDE ION HAS A –2 CHARGE. THE FORMULA FOR IRON III SULFIDE IS Fe2S3.
• (2 x ( +3)) + (3 x (-2)) = 0
IONIC COMPOUNDS CONTAINING POLYATOMIC IONS (CATIONS AND ANIONS)
• LEAD II NITRATE CONSISTS OF ONE LEAD II ION WITH A +2 CHARGE AND TWO NITRATE IONS EACH WITH A –1 CHARGE.
• IN ORDER TO BALANCE THE CHARGES, ONE LEAD II MUST COMBINE WITH TWO NITRATES. THE FORMULA FOR LEAD II NITRATE IS Pb(NO3)2.
• ( +2) + (2 x (-1)) = 0
• AMMONIUM PHOSPHATE CONSISTS OF THREE AMMONIUM IONS EACH WITH A +1 CHARGE AND ONE PHOSPHATE WITH A –3 CHARGE.
• IN ORDER TO BALANCE THE CHARGES, THREE AMMONIUM IONS MUST COMBINE WITH ONE PHOSPHATE. THE FORMULA FOR AMMONIUM PHOSPHATE IS (NH4)3PO4.
• (3 x (+1)) + (-3) = 0
The positive ioncharge without itssign becomes thesubscript of the
negative ion
The negative ion charge without itssign becomes the subscript of the
positive ion1 (+3) + 3(-1) = 0
FORMULAS AND NAMES FOR MOLECULAR COMPOUNDS (COMPOUNDS CONSISTING OF ONLY
NONMETALS, NOT IONS)
• NONMETALS ARE THE ELEMENTS ON THE RIGHT SIDE OF THE PERIODIC TABLE.
• WHEN NAMING COMPOUNDS, PREFIXES ARE USED TO TELL THE NUMBER OF EACH KIND OF ATOM.
• PREFIXES USED
• MONO = 1
• DI = 2
• TRI = 3
• TETRA = 4
• PENTA = 5
• HEXA = 6
• HEPTA = 7
• OCTA = 8
NAMES AND FORMULAS OF MOLECULAR COMPOUNDS
• SULFUR DIOXIDE CONSISTS OF ONE SULFUR ATOM (NO PREFIX IS USED) AND TWO (DI) OXYGEN ATOMS. BOTH SULFUR AND OXYGEN ARE NONMETALS. THE FORMULA FOR SULFUR DIOXIDE IS SO2
• DINITROGEN PENTOXIDE CONSISTS OF TWO NITROGEN ATOMS (DI) AND FIVE OXYGEN ATOMS (PENTA). BOTH NITROGEN AND OXYGEN ARE NONMETALS. THE FORMULA FOR DINITROGEN PENTOXIDE IS N2O5.