Study Guide: Main Group Ions, Transition Metals, Polyatomic Ions, and Ionic vs. Molecular Compounds

Q1. Write the most stable cations from the following main group metals:

Na, Ca, Al, Li, Ba, K

Background

Topic: Main Group Elements – Monoatomic Cations (Type I metal ions)

This question tests your understanding of how main group metals form cations by losing electrons to achieve the electron configuration of the nearest noble gas.

Key Terms and Concepts:

• Cation: A positively charged ion formed when an atom loses electrons.

• Noble Gas Configuration: The stable electron arrangement of noble gases, which main group metals try to achieve when forming cations.

Step-by-Step Guidance

1. Identify the group number of each metal (e.g., Group 1, Group 2, Group 13) to determine how many electrons are lost.

2. Recall that Group 1 metals lose 1 electron, Group 2 lose 2 electrons, and Group 13 lose 3 electrons to achieve noble gas configuration.

3. Write the symbol for each cation, including its charge (e.g., $\text{Na}^+$, $\text{Ca}^{2+}$).

Try solving on your own before revealing the answer!

Q2. Write the most stable anions from the following main group nonmetals:

O, N, F, S, Br, P

Background

Topic: Main Group Elements – Monoatomic Anions

This question tests your understanding of how main group nonmetals gain electrons to achieve the electron configuration of the nearest noble gas.

Key Terms and Concepts:

• Anion: A negatively charged ion formed when an atom gains electrons.

• Noble Gas Configuration: The stable electron arrangement nonmetals aim for when forming anions.

Step-by-Step Guidance

1. Determine the group number for each nonmetal (e.g., Group 15, 16, 17) to find out how many electrons are gained.

2. Recall that Group 17 nonmetals gain 1 electron, Group 16 gain 2 electrons, and Group 15 gain 3 electrons.

3. Write the symbol for each anion, including its charge (e.g., $\text{O}^{2-}$, $\text{F}^-$).

Try solving on your own before revealing the answer!

Q3. Write the most stable cations from the following transition metals:

Cu, Fe, Cr, Ni, Zn, Ag, Cd

Background

Topic: Transition Metals (Type II metal ions)

This question tests your knowledge of common charges for transition metal ions, which can have more than one stable charge.

Key Terms and Concepts:

• Transition Metal Cations: Many transition metals can form more than one stable cation with different charges.

Step-by-Step Guidance

1. Recall the common charges for each transition metal (e.g., Cu can be $\text{Cu}^+$ or $\text{Cu}^{2+}$).

2. Write the symbols for each cation, including all common stable charges.

Try solving on your own before revealing the answer!

Q4. List the names and formulas of common polyatomic ions.

Background

Topic: Polyatomic Ions

This section provides a reference table of polyatomic ions, which are groups of atoms bonded together with an overall charge.

Key Terms and Concepts:

• Polyatomic Ion: A charged group of covalently bonded atoms.

Step-by-Step Guidance

1. Familiarize yourself with the names and formulas of the most common polyatomic ions (e.g., $\text{NO}_3^-$ is nitrate, $\text{SO}_4^{2-}$ is sulfate).

2. Pay attention to ions with similar names but different numbers of oxygen atoms (e.g., sulfate vs. sulfite).

Try reviewing the table and memorizing the most common ions before moving on!

Q5. Predict the empirical formula for ionic compounds formed from the following pairs:

Examples: Na and Cl, Mg and Cl, Al and Cl, Na and S, Mg and S, Al and S, Na and N, Mg and N, Al and N, Fe(II) and Cl, Fe(III) and Cl, Fe(II) and S, Fe(III) and S, Fe(II) and N, Fe(III) and N

Background

Topic: Ionic Compounds and Empirical Formulas

This question tests your ability to write empirical formulas for ionic compounds by balancing the charges of the ions involved.

Key Terms and Concepts:

• Empirical Formula: The simplest whole-number ratio of ions in an ionic compound.

• Charge Balance: The total positive and negative charges must balance to zero in the formula.

Step-by-Step Guidance

1. Write the symbol and charge for each ion involved.

2. Determine the ratio of ions needed so that the total positive and negative charges balance to zero.

3. Write the empirical formula using subscripts to indicate the ratio of ions (e.g., $\text{NaCl}$, $\text{MgCl}_2$).

Try writing the formulas for each pair before checking your answers!

Q6. Predict the empirical formula for ionic compounds formed from the following pairs (polyatomic ions):

Examples: NH4+ and Cl, Na and SO4^2-, NH4+ and S, Mg and SO4^2-, NH4+ and N, Al and SO4^2-, Fe(II) and SO4^2-, Fe(III) and SO4^2-, Fe(II) and NO2^-, Fe(III) and NO2^-, Fe(II) and PO4^3-, Fe(III) and PO4^3-

Background

Topic: Ionic Compounds with Polyatomic Ions

This question tests your ability to write empirical formulas for ionic compounds containing polyatomic ions.

Key Terms and Concepts:

• Polyatomic Ion: A charged group of atoms that acts as a single ion in compounds.

• Empirical Formula: The simplest whole-number ratio of ions in the compound, balancing total charges.

Step-by-Step Guidance

1. Write the symbol and charge for each ion (including polyatomic ions).

2. Balance the total positive and negative charges by adjusting the ratio of ions.

3. Use parentheses around polyatomic ions if more than one is needed in the formula (e.g., $\text{Mg(NO}_3)_2$).

Try writing the formulas for each pair before checking your answers!

Q7. Predict whether the following compounds are ionic or molecular:

CO2, CaF, NH3, SF6, NiCl2, Al(NO3)3, XeF2, N2H2, SCl3, H2O2, KI, BaSO4

Background

Topic: Recognizing Ionic vs. Molecular Compounds

This question tests your ability to distinguish between ionic compounds (formed from metals and nonmetals) and molecular compounds (formed from nonmetals only).

Key Terms and Concepts:

• Ionic Compound: Formed by the transfer of electrons from a metal to a nonmetal.

• Molecular Compound: Formed by the sharing of electrons between nonmetals.

Step-by-Step Guidance

1. Identify whether each compound contains a metal (ionic) or only nonmetals (molecular).

2. Recall that compounds with polyatomic ions are usually ionic, even if they contain nonmetals.

3. Classify each compound as ionic or molecular based on its composition.

Try classifying each compound before checking your answers!