Nomenclature

Nomenclature

High School

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Learning Objectives

• Name ionic compounds, including those with polyatomic ions.

• Understand the prefix system for naming binary covalent compounds.

• Apply IUPAC rules to name basic hydrocarbons, like alkanes and alkenes.

• Recognize and name common acids based on their anion composition.

Key Vocabulary

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IUPAC

A system for naming chemical compounds to ensure each has a unique and specific name.

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Ionic Compound

A compound formed from a metal cation and a non-metal anion through electron transfer.

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Covalent Compound

A compound formed from two non-metals that share electrons to form a chemical bond.

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Alkane

A hydrocarbon containing only single carbon-carbon bonds, which makes the molecule saturated.

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Alkene

A hydrocarbon that contains at least one double carbon-carbon bond, making it unsaturated.

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Alkyne

A hydrocarbon that contains at least one triple carbon-carbon bond, making it unsaturated.

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Rules for Naming Simple Ionic Compounds

• Ionic compounds are formed between a metal (cation) and a nonmetal (anion).

• ​First, name the cation, which keeps the same name as its element.

• Second, name the anion by changing the element's ending to “-ide”.

• For example, the compound CaCl₂ is named Calcium Chloride.

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Solved Example 1
What is the name of the ionic compound formed between aluminum and oxygen?

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Step 1: Analyze and Sketch the Problem

• Goal: Determine the chemical name for the compound formed by aluminum and oxygen.

• Knowns: The compound contains aluminum (Al) and oxygen (O). Aluminum is a metal, and oxygen is a nonmetal.

• Unknown: The systematic name of the resulting ionic compound.

• Rule: Name the metal cation first, then name the nonmetal anion by changing its ending to "-ide".

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Solved Example 1
What is the name of the ionic compound formed between aluminum and oxygen?

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Step 2: Solve for the Unknown

• The metal is aluminum, so the cation name is "aluminum".

• The nonmetal is oxygen. To name the anion, we take the root "ox-" and add the suffix "-ide" to get "oxide".

• Combine the cation and anion names: Aluminum oxide.

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Solved Example 1
What is the name of the ionic compound formed between aluminum and oxygen?

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Step 3: Evaluate the Answer

• The name correctly identifies the metal (Aluminum) and the nonmetal with the proper suffix (Oxide).

• The final name is Aluminum Oxide.

Multiple Choice

According to the rules for naming simple ionic compounds, what is the correct name for the compound Na₂O?

• Disodium Monoxide

• Sodium Oide

• Sodium Oxide

• Sodium(I) Oxide

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Ionic Compounds with Variable Charge

• Some metals, especially transition metals, can form cations with different positive charges.

• A Roman numeral in parentheses shows the specific positive charge of the metal ion.

• For example, Fe²⁺ is named the iron(II) ion, while Fe³⁺ is the iron(III) ion.

• The anion is named with an "-ide" suffix, as in Gold (I) Chloride (AuCl).

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Solved Example 2
Determine the IUPAC name for the ionic compound PbO₂, given that the oxide ion has a charge of 2^-.

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Step 1: Analyze and Sketch the Problem

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Solved Example 2
Determine the IUPAC name for the ionic compound PbO₂, given that the oxide ion has a charge of 2-.

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Step 2: Solve for the Unknown

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Solved Example 2
Determine the IUPAC name for the ionic compound PbO₂, given that the oxide ion has a charge of 2-.

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Step 3: Evaluate the Answer

Multiple Choice

A compound is formed between the Iron (III) ion and the Chloride ion. What is its name and chemical formula?

• Iron (III) Chloride, FeCl₃

• Iron Chloride, FeCl

• Iron (II) Chloride, FeCl₂

• Iron (III) Chloride, Fe₃Cl

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Ionic Compounds with Polyatomic Ions

• Polyatomic ions are groups of covalently bonded atoms that carry a charge.

• Examples include Ammonium (NH₄⁺) and Sulfate (SO₄^2-).

• To name them, the cation is named first, followed by the anion.

• So, CaCO₃ is Calcium Carbonate; Iron(II) with PO₄^3- is Iron(II) Phosphate.

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Solved Example 3
What is the chemical name for the ionic compound composed of aluminum and the sulfate polyatomic ion (SO₄^2-)?

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Step 1: Analyze and Sketch the Problem

• Goal: Determine the IUPAC name for the compound formed by aluminum and sulfate.

• Knowns: The compound contains Aluminum (Al) and the sulfate polyatomic ion (SO₄^2-).

• From the periodic table or common ion charts, Aluminum is in Group 13 and typically forms a cation with a 3+ charge (Al³⁺).

• The sulfate ion is given as SO₄^2-, which has a 2- charge.

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Solved Example 3
What is the chemical name for the ionic compound composed of aluminum and the sulfate polyatomic ion (SO₄^2-)?

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Step 2: Solve for the Unknown

• To form a neutral compound, the total positive charge must equal the total negative charge.

• Find the least common multiple (LCM) of the charges (3 and 2), which is 6.

• To get a total positive charge of +6, we need 2 aluminum ions (2 x +3 = +6).

• To get a total negative charge of -6, we need 3 sulfate ions (3 x -2 = -6).

• The chemical formula is therefore Al₂(SO₄)₃.

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Solved Example 3
What is the chemical name for the ionic compound composed of aluminum and the sulfate polyatomic ion (SO₄^2-)?

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Step 3: Evaluate the Answer

• The cation, Al³⁺, is named from its element: Aluminum. The polyatomic anion, SO₄^2-, has the specific name: Sulfate.

• By naming the cation first, then the anion, the chemical name of the compound is Aluminum Sulfate.

Multiple Choice

What is the correct chemical name for the compound Fe₃(PO₄)₂, which contains a polyatomic ion?

• Iron (II) Phosphate

• Iron Phosphate

• Triiron Diphosphate

• Iron (III) Phosphate

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Naming Binary Covalent Compounds

• Binary covalent compounds are formed between two nonmetal elements.

• The leftmost element is named first; the second element ends in '-ide'.

• Use Greek prefixes for atom counts, but skip 'mono-' for the first element.

• Example: C₂F₄ is Dicarbon Tetrafluoride; SBr₂ is Sulfur Dibromide.

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Solved Example 4
What is the chemical formula for the compound dinitrogen pentoxide?

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Step 1: Analyze and Sketch the Problem

• Goal: Determine the chemical formula from the name.

• Knowns: The name of the compound is dinitrogen pentoxide.

• Unknowns: The chemical symbols and the number of atoms for each element.

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Solved Example 4
What is the chemical formula for the compound dinitrogen pentoxide?

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Step 2: Solve for the Unknown

• Identify the elements from the name. "Nitrogen" corresponds to the symbol N, and "oxide" corresponds to the symbol O.

• Use the Greek prefixes to find the number of atoms for each element. "Di-" means 2 nitrogen atoms and "penta-" means 5 oxygen atoms, giving the formula N₂O₅.

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Solved Example 4
What is the chemical formula for the compound dinitrogen pentoxide?

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Step 3: Evaluate the Answer

• The prefix 'di-' indicates two nitrogen atoms (N₂) and the prefix 'penta-' indicates five oxygen atoms (O₅).

• Combining these parts gives the final chemical formula for dinitrogen pentoxide: N₂O₅.

Multiple Choice

Using the prefix system for binary covalent compounds, what is the name for NH₃?

• Nitrogen Trihydride

• Ammonia

• Nitrogen Hydride

• Mononitrogen Trihydride

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Naming Hydrocarbons: Alkanes

• Alkanes are saturated hydrocarbons with only single bonds between their carbon atoms.

• The base name depends on the longest carbon chain, ending in -ane.

• Number the main chain to give side chains the lowest possible location numbers.

• Example: 3-ethyl-2-methylhexane has a hexane chain with ethyl and methyl side chains.

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Solved Example 5
An alkane has 7 carbon atoms. Using the general formula for alkanes, determine its chemical formula and name.

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Step 1: Analyze and Sketch the Problem

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Solved Example 5
An alkane has 7 carbon atoms. Using the general formula for alkanes, determine its chemical formula and name.

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Step 2: Solve for the Unknown

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Solved Example 5
An alkane has 7 carbon atoms. Using the general formula for alkanes, determine its chemical formula and name.

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Step 3: Evaluate the Answer

Multiple Choice

What is the primary rule for numbering the carbon chain when naming a branched alkane?

• Number the chain based on the size of the alkyl side chains.

• Always number the carbon chain from left to right.

• Number the chain to give the lowest possible numbers to the side chains.

• Number the chain to give the highest possible numbers to the side chains.

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Naming Alkenes and Alkynes

Alkenes

• Contain at least one carbon-carbon double bond (–C=C–).

• Their names end with the suffix "-ene," as in but-2-ene.

• They follow the general formula C_nH_2n.

Alkynes

• Contain at least one carbon-carbon triple bond (–C≡C–).

• Their names end with the suffix "-yne," as in prop-1-yne.

• They follow the general formula C_nH_2n-2.

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Solved Example 6
An alkyne has 5 carbon atoms (pentyne). Using the general formula for alkynes, C_nH_2n-2, what is its molecular formula?

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Step 1: Analyze and Sketch the Problem

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Solved Example 6
An alkyne has 5 carbon atoms (pentyne). Using the general formula for alkynes, C_nH_2n-2, what is its molecular formula?

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Step 2: Solve for the Unknown

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Solved Example 6
An alkyne has 5 carbon atoms (pentyne). Using the general formula for alkynes, C_nH_2n-2, what is its molecular formula?

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Step 3: Evaluate the Answer

Multiple Choice

A hydrocarbon has the general formula C_nH_2n and contains at least one double bond. What is its classification and naming suffix?

• Alkyne, -yne

• Alkane, -ane

• Alkene, -yne

• Alkene, -ene

What are Isomers?

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Chain Isomers

• These isomers have different arrangements of their carbon atom chains.

• They share the exact same molecular formula but have different structures.

• An example is a straight carbon chain versus a branched chain.

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Position Isomers

• These isomers have the same carbon skeleton, but a group’s position differs.

• The molecular formula for each of the position isomers is the same.

• For example, a functional group is attached to a different carbon atom.

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Functional Isomers

• These have the same molecular formula but different functional groups attached.

• This structural difference results in very different chemical and physical properties.

• An example is an alcohol and an ether with identical formulas.

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Solved Example 7
Determine the molecular formula for butane (CH₃CH₂CH₂CH₃) and its isomer, 2-methylpropane. Use the general formula for alkanes, C_nH_2n+2, to verify the molecular formula for butane.

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Step 1: Analyze and Sketch the Problem

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Solved Example 7
Determine the molecular formula for butane (CH₃CH₂CH₂CH₃) and its isomer, 2-methylpropane. Use the general formula for alkanes, C_nH_2n+2, to verify the molecular formula for butane.

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Step 2: Solve for the Unknown

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Solved Example 7

Determine the molecular formula for butane (CH₃CH₂CH₂CH₃) and its isomer, 2-methylpropane. Use the general formula for alkanes, C_nH_2n+2, to verify the molecular formula for butane.

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Step 3: Evaluate the Answer

• We have successfully determined the molecular formula for both compounds is C₄H₁₀.

• Because they share the same molecular formula but have different structures (butane is a straight-chain alkane and 2-methylpropane is a branched-chain alkane), they are correctly identified as isomers.

Multiple Choice

What is the defining characteristic of isomers?

• They have identical physical and chemical properties.

• They have the same molecular formula but a different structure.

• They have the same structure but a different molecular formula.

• They have different numbers of atoms and different structures.

Naming Acids

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Anion ends in -ide

• The acid is named with the prefix 'hydro-' and the suffix '-ic'.

• The root of the anion's name is placed between the prefix and suffix.

• Example: HCl, where the anion is Chloride, becomes Hydrochloric acid.

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Anion ends in -ite

• The '-ite' suffix of the anion is replaced with the suffix '-ous'.

• This is followed by the word 'acid' to complete the name.

• Example: H₂SO₃, with anion Sulfite, is named Sulfurous acid.

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Anion ends in -ate

• The '-ate' suffix of the anion is replaced with the suffix '-ic'.

• The name is completed by adding the word 'acid' after the new name.

• Example: H₂SO₄, with anion Sulfate, is named Sulfuric acid.

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Solved Example 8
What is the chemical name for an acid with the formula H₃PO₄, given that the polyatomic anion PO₄^3- is named 'phosphate'?

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Step 1: Analyze and Sketch the Problem

• Goal: To find the name of the acid H₃PO₄.

• Knowns: The anion is PO₄^3-, which is named 'phosphate'.

• Unknown: The chemical name for the acid H₃PO₄.

• Formula: The naming rule for anions ending in '-ate' is to change the suffix to '-ic acid'.

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Solved Example 8
What is the chemical name for an acid with the formula H₃PO₄, given that the polyatomic anion PO₄^3- is named 'phosphate'?

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Step 2: Solve for the Unknown

• Start with the anion name: phosphate.

• Change the '-ate' suffix to '-ic': phosphoric.

• Add the word 'acid': Phosphoric acid.

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Solved Example 8
What is the chemical name for an acid with the formula H₃PO₄, given that the polyatomic anion PO₄^3- is named 'phosphate'?

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Step 3: Evaluate the Answer

• The chemical name for H₃PO₄ is Phosphoric acid.

• This follows Rule 3 for naming acids, as the anion 'phosphate' ends in '-ate'.

Multiple Choice

An acid is formed with the polyatomic anion nitrate (NO₃^-). Based on the naming rules, what is the name of the acid HNO₃?

• Nitrate Acid

• Nitrous Acid

• Hydronitric Acid

• Nitric Acid

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Common Naming Misconceptions

Misconception	Correction
Roman numerals are needed for all metal compounds.	Only for metals with several ion types, like Fe2+ and Fe3+.
Prefixes like 'di-' and 'tri-' are used for all compounds.	Prefixes are for naming covalent compounds, not ionic ones.
The longest carbon chain is always drawn horizontally.	The longest chain can bend; trace all paths to find the true longest one.

Multiple Choice

What are the correct names for the ionic compound made of magnesium and sulfur (MgS) and the covalent compound P₂O₅?

• Magnesium Sulfide and Diphosphorus Pentoxide

• Magnesium Sulfide and Phosphorus(V) Oxide

• Monomagnesium Sulfide and Diphosphorus Pentoxide

• Magnesium(II) Sulfide and Phosphorus Oxide

Multiple Choice

Why is a molecule with the formula C₅H₁₀ classified as an alkene according to its general formula?

• It follows the C_nH_2n+2 formula, characteristic of alkanes.

• It follows the C_nH_2n-2 formula, characteristic of alkynes.

• It follows the C_nH_2n formula, characteristic of alkenes.

• It contains exactly five carbon atoms.

Multiple Choice

Based on IUPAC rules, predict the chemical formula for a compound formed between the Iron(III) ion and the Carbonate ion (CO₃^2-).

• Fe₂(CO₃)₃

• Fe₃(CO₃)₂

• Fe(CO₃)₂

• Fe(CO₃)

Multiple Choice

The name '2-ethylbutane' is incorrect. Analyze the structure this name implies and determine the correct IUPAC name for the molecule.

• 2-methylpentane

• Hexane

• 2-ethylbutane is correct

• 3-methylpentane

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Summary

• Name ionic compounds by cation and anion, using Roman numerals for variable-charge metals.

• Polyatomic ions have specific names that are used in the compound's name.

• Binary covalent compounds use Greek prefixes to indicate the number of each atom.

• Name hydrocarbons by carbon chain length and bond type, and acids by anion suffix.

Poll

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