Writing ionic formulas
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WRITING IONIC FORMULAS PowerPoint PPT Presentation


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WRITING IONIC FORMULAS. Write the symbol for the cation, then the symbol for the anion. Balance the charges - use the crisscross method - by placing subscripts and “( )” for polyatomic ions if needed. Monatomic ions don’t need “( )”.

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WRITING IONIC FORMULAS

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Writing ionic formulas

WRITING IONIC FORMULAS

  • Write the symbol for the cation, then the symbol for the anion.

  • Balance the charges - use the crisscross method - by placing subscripts and “( )” for polyatomic ions if needed.

  • Monatomic ions don’t need “( )”.

  • Net charges must be zero. Use ion sheet to get charges.


Determining the charge

DETERMINING THE CHARGE

Monotomic Ions

  • An ion with only one atom; Mg+2, Na+1, O-2

  • Most of the charges can be determined by the atom’s position on the periodic table.

  • It is the atom’s oxidation number.

  • Most transition elements have more than one oxidation number (see back of PT or cover of textbook)


Determining the charge1

DETERMINING THE CHARGE

Polyatomic Ions

  • An ion made up of more than one atom NH4+1, SO4-2, C2H3O2-1;

  • The charges given to polyatomic ions apply to the whole group of atoms.

  • NEVER change the subscripts of a polyatomic ion.

  • If more than one ion is needed, a parenthesis is placed around the ion and the subscript is written outside; Example: Al(OH)3


Criss cross for writing formulae

Criss Cross for writing formulae

  • Determine the charges on the atoms in the formula

  • +ve Cation listed first and –ve Anion listed second

  • Criss Cross the charge each and use the charge as the subscript of the other.


Writing ionic formulas

Ex. Aluminum chloride. Al and Cl.

  • What charge does Al get? +3 Cl ? -1

  • Let’s write them down

    Al3+ Cl1- Al3 Cl1 Don’t need to record “1”s

  • Step 2 to get the neutral formula AlCl3

  • Check to see if formula is neutral

    +3 -1 -1 -1 = 0

  • Remember that if you have a polyatomic ion there will be a few atoms grouped together that have a charge together. So use parenthesis.


Multiple oxidation numbers

MULTIPLE OXIDATION NUMBERS

Cations can have more than one oxidation number.

Example: Cu+1 and Cu+2.

It is important to distinguish which ion is in the compound.

There are two ways used in chemistry.


Multiple oxidation numbers1

MULTIPLE OXIDATION NUMBERS

Stock SystemClassical (Latin)

Cu+1 copper (I)cuprous

Cu+2 copper (II)cupric

Sn+2 tin(II)stannous

Sn+4 tin (IV)stannic

Hg2+2 mercury (I)mercurous

Hg+2 mercury (II)mercuric

The lower charge ends in –ous and the higher charge ends in –ic.


Multiple oxidation numbers2

MULTIPLE OXIDATION NUMBERS

You are only responsible for only the Stock system but I just wanted you to see the other.


Multiple oxidation numbers3

MULTIPLE OXIDATION NUMBERS

You are only responsible in class for the Stock system but I wanted to make you familiar with the classic.


Examples

Examples

cupric sulfate/copper (II) sulfateCuSO4

ferrous oxide/iron (II) oxide

FeO

cobaltic chloride/cobalt (III) chloride

CoCl3

mercurous nitrate/mercury (I) nitrate

Hg2(NO)2


Practice

PRACTICE

  • lithium fluoride

  • magnesium chloride

  • calcium bromide

  • lithium iodide

  • lithium oxide

  • calcium sulfate

  • barium cyanide

  • Iron (II) oxide

  • barium sulfate

  • aluminum oxide


Practice1

PRACTICE

  • sodium nitrate

  • iron(III) sulfate

  • copper (II) sulfite

  • tin (IV) fluoride


Practice2

PRACTICE

  • lithium fluorideLiF

  • magnesium chlorideMgCl2

  • calcium bromideCaBr2

  • lithium iodideLiI

  • lithium oxideLi2O

  • calcium sulfateCaSO4

  • barium cyanideBaCN

  • Iron (II) oxideFeO

  • barium sulfateBaSO4

  • aluminum oxide Al2O3


Practice3

PRACTICE

  • sodium nitrateNaNO3

  • iron(III) sulfateFe2(SO4)3

  • copper (II) sulfiteCuSO3

  • tin (IV) fluorideSnF4


Writing formulas

WRITING FORMULAS

  • Potassium fluoride

  • Potassium iodide

  • Potassium iodate 11. Iron (II) hydroxide

  • Beryllium chloride 12. Iron (III) oxalate

  • Beryllium oxide.

  • Beryllium nitride

  • Beryllium hydroxide

  • Sodium acetate

  • Sodium sulfate

  • Copper (II) sulfate


Putting it altogether

Putting It Altogether

You need to make sure that you can distinguish between ionic, covalent, and acid compounds.


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