11/13/2010 Naming and Writing Formulas A Review Activity for Panther-Chemists.

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Naming and Writing FormulasA Review Activity for Panther-Chemists

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What do you want to do?

• Determine whether a compound is ionic or covalent

• Write a chemical formula given a word name• Write a word name given a chemical formula• Translate a chemical reaction from symbols to

words• Translate a chemical reaction from words to s

ymbols

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How to determine whether a compound is ionic or covalent

• First, grab your periodic table and ion sheet. When you are ready, you may continue…

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• Find the zigzag line on your periodic table (it is in the “p-block”)

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• Recall that metals are located to the left of the zigzag line

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• …and nonmetals are located to the left of the zigzag

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• If a compound is made of a metal and nonmetal, it is ionic; the metal ion always appears first in a chemical name

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• If a compound is made of all nonmetals, it is covalent

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• Practice Problems: Determine whether each formula is ionic or covalent

• Calcium chloride

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• Calcium chloride Ionic

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• Aluminum phosphate

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• Aluminum phosphate Ionic

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• Carbon tetrachloride

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• Carbon tetrachloride CovalentC

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• Mercury (II) sulfate

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• Mercury (II) sulfate Ionic

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• Ammonium chloride

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• Ammonium chloride Ionic; because ammonium is a positively charged ion (polyatomic cation found on ion sheet)

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• Disulfur pentoxide

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• Disulfur pentoxide Covalent

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How to write a formula given a name

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• Step 1: Determine whether the compound is ionic or covalent ; if covalent, use prefixes and stop here. If ionic, continue through step 5. [click here if you need a refresher on how to decide whether a compound is ionic or covalent]

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• Step 1: Determine whether the compound is ionic or covalent; if covalent, use prefixes and stop here. If ionic, continue through step 5.

• Step 2: Split name into two pieces, usually after the first word

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• Step 3: Write the ions for each piece

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• Step 3: Write the ions for each piece• Step 4: Drop + and – signs, then criss-cross

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• Step 3: Write the ions for each piece• Step 4: Drop + and – signs, then criss-cross• Step 5: Add parenthesis if needed and see if

the formula can be reduced

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• Ready for practice? Try to write the given formulas. When you have an answer, click through to check your work. Continue to the next page…

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How to write a formula given a name• Step 1: Determine whether the compound is ionic or covalent ; if covalent, use prefixes and stop here. If ionic, continue through step

5.• Step 2: Split name into two pieces, usually after the first word• Step 3: Write the ions for each piece• Step 4: Drop + and – signs, then criss-cross• Step 5: Add parenthesis if needed and see if the formula can be reduced

PRACTICE PROBLEMS: Write the formula for barium chloride.

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PRACTICE PROBLEMS: Write the formula for barium chloride.• Step 1: Ionic, because the first part of the name, barium, is a metal

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PRACTICE PROBLEMS: Write the formula for barium chloride.• Step 1: Ionic, because the first part of the name, barium, is a metal• Step 2: barium / chloride

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PRACTICE PROBLEMS: Write the formula for barium chloride.• Step 1: Ionic, because the first part of the name, barium, is a metal• Step 2: barium / chloride• Step 3: Ba2+ / Cl- (note: use your periodic table to determine charges

of individual elements; use your ion sheet to write out polyatomic ions)

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of individual elements; use your ion sheet to write out polyatomic ions)• Step 4:

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of individual elements; use your ion sheet to write out polyatomic ions)• Step 4:• Step 5:

Parenthesis are only needed when a polyatomic ion has a subscript (number) greater than 1. The ion ratio 1Ba:2Cl can not be reduced.

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PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.

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PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.• Step 1: Ionic, because the first part of the name, copper, is a metal

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PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.• Step 1: Ionic, because the first part of the name, copper, is a metal• Step 2: copper (II) / sulfate

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PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.• Step 1: Ionic, because the first part of the name, copper, is a metal• Step 2: copper (II) / sulfate• Step 3: Cu2+ / SO4

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PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.• Step 1: Ionic, because the first part of the name, copper (II), is a metal• Step 2: copper (II) / sulfate• Step 3: Cu2+ / SO4

2- (note: the Roman numeral (II) indicates the charge of the copper ion, 2+; the ‘sulfate’ ion is on your ion sheet)

• Step 4:

• Notice how nothing happened to the “4” on the sulfate ion. DO NOT modify numbers that are AREADY there as subscripts (numbers on the bottom) before the criss-cross (already there at Step 3 in ion form).

Cu SO4

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2 + -2

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Cu SO4

PRACTICE PROBLEMS: Write the formula for copper (II) sulfate.• Step 1: Ionic, because the first part of the name, copper (II), is a metal• Step 2: copper (II) / sulfate• Step 3: Cu2+ / SO4

2- (note: the Roman numeral (II) indicates the charge of the copper ion, 2+; the ‘sulfate’ ion is on your ion sheet)

• Step 4:

• Step 5: For now, you will need parenthesis around the sulfate ion because it is a polyatomic ion that received a subscript greater than 1.

• Also, the ion ratio is 2Cu: 2 SO4 which can reduce to 1:1… now you can remove the parenthesis

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PRACTICE PROBLEMS: Write the formula for sulfur trioxide.

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PRACTICE PROBLEMS: Write the formula for sulfur trioxide.• Step 1: Covalent, because the formula contains all nonmetals… 1 sulfur

and three oxygens = SO3… no criss-crossing for covalent compounds. 1 = mono2 = di3 = tri4 = tetra5 = penta6 = hexa7 = hepta8 = octa9 = nona10 = deca

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PRACTICE PROBLEMS: Write the formula for calcium phosphate.

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PRACTICE PROBLEMS: Write the formula for calcium phosphate.• Step 1: Ionic, because the first part of the name, calcium, is a metal

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PRACTICE PROBLEMS: Write the formula for calcium phosphate.• Step 1: Ionic, because the first part of the name, calcium, is a metal• Step 2: calcium / phosphate

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PRACTICE PROBLEMS: Write the formula for calcium phosphate.• Step 1: Ionic, because the first part of the name, calcium, is a metal• Step 2: calcium / phosphate• Step 3: Ca 2+ / PO4

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• Step 4:Ca PO4

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+ -2 3

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• Step 4:

• Step 5: Because phosphate is a polyatomic ion that received a subscript greater than 1, use parenthesis. The ion ratio is 3Ca: 2PO4; you can not reduce this ratio.

Ca (PO4)

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How to write a name from a formula

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How to write a name from a formula

• Step 1: Determine whether the formula is ionic or covalent [if you need help with this step, click here]

• Step 2: Apply appropriate naming rules…-If covalent, use prefixes except for ‘mono’ on first element-If ionic, split formula into 2 pieces (usually split after first ion). First ion gets its ‘regular’ name… 2nd ion changes ending to –ide if monatomic, or is found on anion side of ion sheet if polyatomic. Check cations on ion sheet for Roman numerals.

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How to write a name from a formula• Step 1: Determine whether the formula is ionic or covalent• Step 2: Apply appropriate naming rules…

-If covalent, use prefixes except for ‘mono’ on first element-If ionic, split formula into 2 pieces (usually split after first ion). First ion gets its ‘regular’ name… 2nd ion changes ending to –ide if monatomic, or is found on anion side of ion sheet if polyatomic. Check cations on ion sheet for Roman numerals.

Practice problem: Name Cu(OH)2

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• Step 1: Ionic

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• Step 1: Ionic• Step 2: Cu / (OH)2

• First part is named ‘COPPER’• Second part is found on anion side of ion sheet, called ‘HYDROXIDE’• According to cations on ion sheet, copper needs a Roman numeral (can be I or II)• Backwards criss-cross to determine original ion charges in order to identify correct

Roman numeral• Check anion on ion sheet

to verify ions are correct• Copper used to have 2+ charge, therefore, this is copper (II) hydroxide

Cu OH( )2

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Practice problem: Name NO2

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Practice problem: Name NO2

• Step 1: Covalent• Step 2: Do not use the prefix ‘mono’ for first element… 1N = nitrogen; 2O =

dioxide… therefore, this is nitrogen dioxide

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Practice problem: Name N2O5

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Practice problem: Name N2O5

• Step 1: Covalent• Step 2: Do not use the prefix ‘mono’ for first element… 1N = nitrogen; 2O =

dioxide… therefore, this is nitrogen dioxide

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When a polyatomic ion DOES NOT have parenthesis, you MAY NOT move its subscript for a backwards criss-cross!

Practice problem: Name FePO4

• Step 1: Ionic• Step 2: Fe / PO4

• First part is named ‘IRON’• Second part is found on anion side of ion sheet, called ‘PHOSPHATE’• According to cations on ion sheet, iron needs a Roman numeral (can be II or III)• Backwards criss-cross to determine original ion charges … note there are no

parenthesis around phosphate so the 4 stays in place: Fe / PO4

• Check anion on ion sheet to verify ions are correct… phosphate’s charge of 3- must have cancelled out… the original formula must have looked like this: Fe3(PO4)3

• Iron used to have 3+ charge, therefore, this is iron (III) phosphate11/13/2010

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Practice problem: Name Al2O3

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Practice problem: Name Al2O3

• Step 1: Ionic• Step 2: Al2 / O3

• First ion is called ‘Aluminum’• Second ion is monatomic so it changes its ending to –ide… ‘oxide’• Aluminum does not need a Roman numeral according to the cations on the ion

sheet• Therefore, this is called aluminum oxide

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How to translate a chemical reaction from symbols to words

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• Step 1: Make sure the reaction is balanced. If it is not balanced, take a minute to balance it.

• Step 2: Recall that coefficients in a reaction indicate the number of moles. When there are ‘invisible 1’ coefficients, translate them as “one mole of…”

• Step 3: States of matter generally sound best written before a compound; except for ‘gas’, which sounds best after a compound

• Step 4: Review naming rules if you need a refresher• Common symbols:

(s) = solid → = produces; yields; reacts to form; etc.(l) = liquid → = when heated, produces… (g) or (↑) = gas (aq) = aqueous (dissolved in water; solution)(ppt) or (↓) = precipitate

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• Step 1: Make sure the reaction is balanced. If it is not balanced, take a minute to balance it.• Step 2: Recall that coefficients in a reaction indicate the number of moles. When there are ‘invisible 1’ coefficients,

translate them as “one mole of…”• Step 3: States of matter generally sound best written before a compound; except for ‘gas’, which sounds best after a

compound• Step 4: Review naming rules if you need a refresher• Common symbols:

Practice Problem: Translate 4Fe(s) + 3O2(g) → 2Fe2O3 (s)

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Practice Problem: Translate 4Fe(s) + 3O2(g) → 2Fe2O3 (s)

• Step 1: balanced• Step 2, 3, 4:

Four moles solid iron plus three moles oxygen gas produce two moles solid iron (III) oxide.

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Practice Problem: Translate C6H12O6(s) + 9O2(g) → 6CO2(g) + 6H2O(g)

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Practice Problem: Translate C6H12O6(s) + 9O2(g) → 6CO2(g) + 6H2O(g)

• Step 1: balanced• Step 2, 3, 4:

One mole solid sugar plus nine moles oxygen gas react to form six moles carbon dioxide gas and six moles water vapor.

• It is OK to use the common name of familiar chemicals like sugar, water, ammonia (NH3), etc.

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How to translate a chemical reaction from words to symbols

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• Step 1: It is helpful to circle or underline chemical formulas first• Step 2: Translate chemical names to formulas; review naming rules if you need a refresher;

remember that HONFIBrCl make diatomic molecules when they are not in a compound• Step 3: States of matter are always written after the chemical formula• Step 4: Balance the reaction

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• Step 1: It is helpful to circle or underline chemical formulas first• Step 2: Translate chemical names to formulas; review naming rules if you need a refresher;

remember that HONFIBrCl make diatomic molecules when they are not in a compound• Step 3: States of matter are always written after the chemical formula• Step 4: Balance the reaction

Practice problem: Solid potassium chlorate, when heated, decomposes to produce liquid potassium chloride and oxygen gas.

• Step 1: Circle chemical formulas• Step 2: Translate names to formulas• Step 3: KClO3(s) → KCl(l) + O2(g)

• Step 4: 2KClO3(s) → 2KCl(l) + 3O2(g)

KCl O2

11/13/2010 Naming and Writing Formulas A Review Activity for Panther-Chemists.

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