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Ms. Reynolds

MacArthur High School: (516) 434-7225

Ms. Reynolds

:

Formula Writing

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Formula Writing
Formula Writing notes:

Rules:

1.  represent each kind of element in a compound with the correct symbol for that element

2.  use subscripts to indicate the number of  atoms of each element of the compound.  If one atom is present, no subscript is used

3. write the symbol for the element with the lower electronegativity first, then the element with the higher electronegativity. This is the same as the + ion first, the – ion second.

 

Criss cross method:

· assign an oxidation number (What ion will the element make when it completes it's outer shell?)

· criss-cross the oxidation #

· drop the sign

· reduce if necessary

 

Naming Compounds

binary compound:

· has 2 elements

      EX: H2O

tertiary compound:

· has 3 elements (look at Table E for the Polyatomic Ion)

EX: H2SO4

 

Binary compounds:

the metal keeps it's name, change the last element to -IDE

EX:  sodium + chlorine
sodium chloride

 

Polyatomics

· An element combined with a polyatomic ion found on Table E Everyone keeps their name

EX: Calcium + Carbonate 

           Ca     +     (CO3)

Calcium Carbonate

 

Stock System

· Used when a metal has more than one oxidation state

.Oxidation state used will be in Roman numerals in parenthesis.

EX: iron (III) oxide

Fe+3 O-2 = Fe2O3

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