Naming Ionic Compounds Answer Key Pogil

Naming Ionic Compounds: A Comprehensive Guide with Answers

Ionic compounds are formed through the electrostatic attraction between oppositely charged ions—cations (positive ions) and anions (negative ions). Mastering the nomenclature (naming) of these compounds is crucial for anyone studying chemistry. This comprehensive guide will walk you through the process, providing explanations, examples, and ultimately, an answer key for common POGIL (Process Oriented Guided Inquiry Learning) activities focusing on ionic compound naming.

Understanding the Basics: Cations and Anions

Before diving into naming, let's solidify our understanding of the building blocks:

Cations: The Positively Charged Ions

Cations are formed when an atom loses one or more electrons, resulting in a positive charge. The most common cations are derived from metals. Their names usually reflect the name of the element. For example:

• Na⁺: Sodium ion
• K⁺: Potassium ion
• Ca²⁺: Calcium ion
• Fe²⁺: Iron(II) ion (Note: Roman numerals indicate the charge)
• Fe³⁺: Iron(III) ion (Note: Roman numerals indicate the charge)

Notice the use of Roman numerals for transition metals (like iron) and some post-transition metals. This is because these elements can form multiple cations with different charges. The Roman numeral specifies the charge of the cation in the compound.

Anions: The Negatively Charged Ions

Anions are formed when an atom gains one or more electrons, resulting in a negative charge. These are often derived from nonmetals. Their names typically end in "-ide". For example:

• Cl⁻: Chloride ion
• O²⁻: Oxide ion
• S²⁻: Sulfide ion
• N³⁻: Nitride ion
• P³⁻: Phosphide ion

Naming Ionic Compounds: A Step-by-Step Approach

Naming ionic compounds involves systematically combining the names of the cation and the anion. Let's break down the process:

1. Identify the cation and anion: First, determine the constituent ions making up the compound. This often involves understanding chemical formulas and recognizing common ions.

2. Name the cation: Write down the name of the cation. Remember to use Roman numerals for transition metals and some post-transition metals to indicate their charge.

3. Name the anion: Write down the name of the anion, ending it with "-ide."

4. Combine the names: Combine the names of the cation and anion, with the cation's name appearing first.

Examples:

• NaCl: Sodium chloride (Na⁺ is sodium, Cl⁻ is chloride)
• K₂O: Potassium oxide (K⁺ is potassium, O²⁻ is oxide)
• CaCl₂: Calcium chloride (Ca²⁺ is calcium, Cl⁻ is chloride)
• FeO: Iron(II) oxide (Fe²⁺ is iron(II), O²⁻ is oxide)
• Fe₂O₃: Iron(III) oxide (Fe³⁺ is iron(III), O²⁻ is oxide)
• Cu₂S: Copper(I) sulfide (Cu⁺ is copper(I), S²⁻ is sulfide)
• CuS: Copper(II) sulfide (Cu²⁺ is copper(II), S²⁻ is sulfide)

Polyatomic Ions: Adding Complexity

Polyatomic ions are groups of atoms that carry an overall charge. These add a layer of complexity to ionic compound naming but follow a similar principle. Here are some common polyatomic ions:

• OH⁻: Hydroxide ion
• NO₃⁻: Nitrate ion
• SO₄²⁻: Sulfate ion
• CO₃²⁻: Carbonate ion
• PO₄³⁻: Phosphate ion
• NH₄⁺: Ammonium ion

When naming compounds containing polyatomic ions, simply substitute the name of the polyatomic ion into the naming process. No need to change the endings.

Examples:

• NaOH: Sodium hydroxide (Na⁺ is sodium, OH⁻ is hydroxide)
• KNO₃: Potassium nitrate (K⁺ is potassium, NO₃⁻ is nitrate)
• CaSO₄: Calcium sulfate (Ca²⁺ is calcium, SO₄²⁻ is sulfate)
• (NH₄)₂SO₄: Ammonium sulfate (NH₄⁺ is ammonium, SO₄²⁻ is sulfate)
• Fe(NO₃)₃: Iron(III) nitrate (Fe³⁺ is iron(III), NO₃⁻ is nitrate)

Hydrates: Incorporating Water Molecules

Hydrates are ionic compounds that incorporate water molecules into their crystal structure. These water molecules are indicated in the chemical formula using a dot (·) followed by the number of water molecules. When naming hydrates, you add the prefix "hydrate" along with a numerical prefix indicating the number of water molecules.

Examples:

• CuSO₄·5H₂O: Copper(II) sulfate pentahydrate (5 water molecules)
• CoCl₂·6H₂O: Cobalt(II) chloride hexahydrate (6 water molecules)
• MgSO₄·7H₂O: Magnesium sulfate heptahydrate (7 water molecules)

Common Prefixes for Hydrates

Number of Water Molecules	Prefix
1	Mono-
2	Di-
3	Tri-
4	Tetra-
5	Penta-
6	Hexa-
7	Hepta-
8	Octa-
9	Nona-
10	Deca-

Answer Key for POGIL Activities (Illustrative Examples)

This section provides example answers, keeping in mind that POGIL activities often involve a series of questions designed to guide students through the learning process. The specific questions and answers will vary depending on the POGIL activity used. These examples represent a typical range of questions and answers you might encounter.

POGIL Activity Example 1:

Question 1: Name the following ionic compound: Li₂S

Answer 1: Lithium sulfide

POGIL Activity Example 2:

Question 1: What is the name of the ionic compound formed by combining calcium ions (Ca²⁺) and chloride ions (Cl⁻)?

Answer 1: Calcium chloride

POGIL Activity Example 3:

Question 1: Write the name for the compound with the formula FeCl₃.

Answer 1: Iron(III) chloride

POGIL Activity Example 4:

Question 1: Name the following compound: (NH₄)₃PO₄

Answer 1: Ammonium phosphate

POGIL Activity Example 5:

Question 1: What is the name of the hydrate with the formula CrCl₃·6H₂O?

Answer 1: Chromium(III) chloride hexahydrate

POGIL Activity Example 6:

Question 1: Provide the chemical formula for potassium iodide.

Answer 1: KI

POGIL Activity Example 7:

Question 1: What is the name and formula of the ionic compound formed from magnesium ions (Mg²⁺) and nitrate ions (NO₃⁻)?

Answer 1: Magnesium nitrate, Mg(NO₃)₂

POGIL Activity Example 8 (More Complex):

Question 1: A compound is analyzed and found to contain 26.58% potassium, 35.35% chromium, and 38.07% oxygen. Determine the empirical formula and then name the compound.

Answer 1: This requires calculating the moles of each element, finding the simplest whole number ratio, and then identifying the ions involved. The empirical formula would be K₂Cr₂O₇ and the name is Potassium dichromate. This requires stoichiometric calculations beyond basic naming, showing the application of naming conventions in a more complex scenario.

POGIL Activity Example 9 (Incorporating Multiple Concepts):

Question 1: Explain the difference between naming an ionic compound containing a transition metal and naming an ionic compound containing an alkali metal. Give examples to support your explanation.

Answer 1: Transition metals have variable oxidation states (charges), so Roman numerals are used to specify the charge of the metal cation in the compound’s name. Alkali metals always have a +1 charge, so their charge doesn’t need to be specified. For example: Iron(II) oxide (FeO) vs. Sodium oxide (Na₂O). The use of Roman numerals in the former shows the charge of the iron ion, unlike sodium, which always has a +1 charge.

These examples illustrate the different levels of complexity encountered in POGIL activities. Remember to consult the specific questions within your POGIL activity to find the relevant answers. This guide provides a robust foundation for understanding and applying the principles of ionic compound nomenclature. By systematically following the steps and understanding the exceptions, you will be well-equipped to tackle any POGIL activity or other challenges related to naming ionic compounds.