Naming Chemical Compounds

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Ions: Naming and Formulas

Cations (positive charge)

• Single ion formation– Metals in groups 1,2,13– Element Name + ion– ex. Ca+2 Calcium ion

• Multiple ion formation - Transition metals, Tin and Lead- Element Name (RN) + ion

- Roman Numeral (RN) = charge

- ex. Fe+3 Iron (III) ion

Anions (negative charge)• Nonmetals

– Root of Element –ide– ex. S-2 sulfide

• Formulas -- element symbol AND charge • Charge is determined by group number or roman numeral

Naming:

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Naming Binary Compounds – 2 Elements

• Cation/1st element = name of element (always 1st)• Anion/2nd element = root of element + ide

– Type I (Ionic) – cation only forms a single ion….• Nothing added

– Type II (Ionic) - cation forms multiple ions….. • roman numeral must be added (between cation and anion

names) to indicate charge of the metal

– Type III (covalent) – 1st element is a nonmetal … • Prefixes are used to indicate number of atoms for 1st and 2nd

element • Mono- never used on 1st element 3

Type I (binary ionic)

• Characteristics– 2 elements– Metal + Nonmetal– Metal found in groups 1,2,13,Zn+2,Ag+,Cd+2

• Rules– cation (+) named 1st, anion (-) named second– cation element name– anion root of element name + (-ide)

*subscripts of chemical formulas are NOT indicated directly in compound name

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Type II (binary ionic)

• Characteristics– 2 elements– Metal + Nonmetal– Metal found in groups 3-12,Pb,Sn

• Rules– cation (+) named 1st, anion (-) named second– cation element name (roman numeral)

• roman numeral indicates the charge of the cation

– anion root of element name + (-ide)*subscripts of chemical formulas are NOT indicated directly in compound name

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Determining Charge for Roman Numerals

• Total charge of + ions and – ions = 0 (# +ions)(charge +ions) + (# -ions)(charge –ions) = 0

Example: FeCl2 --- (1) Fe ion + (2 Cl)(-1) = 0

Fe ion + (-2) = 0 Fe ion = 2+

Cr2O3 ----- (2) Cr ion + (3 O) (-2) = 0 2 Cr ions + (- 6) = 0

2 Cr ions = 6+ Cr ion = 3+ = Cr3+

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Type III (binary covalent)• Characteristics

– 2 elements– Nonmetal + Nonmetal

• Rules– 1st element element name– 2nd element root of element name + (-ide)– Use prefixes on both elements to indicate the number

of atoms (subscripts)• 1 (mono) 2 (di) 3 (tri) 4 (tetra) 5 (penta)

6 (hexa) 7 (hepta) 8 (octa) 9 (nona) 10 (deca)• NEVER use (mono) on the 1st element• No double vowels with “o” and “a” 7

Non-binary Ionic• Characteristics

– 3 or more elements– contains a polyatomic ion

• Rules– Cation

• Metal (groups 1,2,13,Zn+2,Ag+,Cd+2) element name• Metal (groups 3-12, Pb, Sn) element name (roman numeral)• Polyatomic ion name on reference sheet

– Anion • Nonmetal root of element name + (-ide)• Polyatomic ion name on reference sheet

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Writing Formulas

Elements and Compounds

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Element Formulas

• Monatomic Elements– Only the element symbol is used for the formula

• Diatomic Elements– These elements can NOT exist in nature as single

atoms, they must be paired.– They include: hydrogen (H2), nitrogen (N2), oxygen

(O2), fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2).

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Compound Formulas - Ionic• Ionic (metal and nonmetal)

– Symbol• Elements – symbol on periodic table• Polyatomic ions – reference sheet

– Charges• Group charges – 1(+1), 2(+2), 13(+3), 15(-3), 16(-2), 17(-1)• Roman numerals – charge of the transition metal• Polyatomic ions – reference sheet

– Switch• total (+) = total (-)• Charge #’s cross down to become the subscripts on the other

element– Reduce

• Subscripts must be in smallest ratios11

Compound Formulas – Covalent • Covalent (only nonmetals)

– Convert prefixes to subscripts– place BEHIND the element symbol• Mono – 1• Di – 2• Tri – 3• Tetra – 4• Penta – 5• Hexa – 6• Hepta -7• Octa – 8• Nona – 9• Deca - 10

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