Problem 59 - Chemistry: The Central Science in SI Units, Global Edition

Question

Predict whether each of the following oxides is ionic or molecular: \(\mathrm{ZnO}, \mathrm{K}_{2} \mathrm{O}, \mathrm{SO}_{2}, \mathrm{OF}_{2}, \mathrm{TiO}_{2}\)

Step-by-Step Solution

Answer

The given oxides can be classified as follows: \(ZnO\): Ionic \(K_2O\): Ionic \(SO_2\): Molecular \(OF_2\): Molecular \(TiO_2\): Ionic

Step 1: Identify the component elements and their electronegativities

Check the periodic table for the electronegativity values of the elements in each oxide: Zn: 1.65 (metal) O: 3.44 (nonmetal) K: 0.82 (metal) S: 2.58 (nonmetal) F: 3.98 (nonmetal) Ti: 1.54 (metal)

Step 2: Determine the electronegativity differences for each oxide

Calculate the difference in electronegativity values for each oxide: ZnO: 3.44 - 1.65 = 1.79 K2O: 3.44 - 0.82 = 2.62 SO2: 3.44 - 2.58 = 0.86 OF2: 3.98 - 3.44 = 0.54 TiO2: 3.44 - 1.54 = 1.90

Step 3: Categorize the oxides as ionic or molecular based on electronegativity differences

Determine if each oxide is ionic or molecular based on their electronegativity differences. If the difference is greater than 1.7, it is generally considered ionic. Otherwise, it is molecular: ZnO: 1.79 > 1.7 => ionic K2O: 2.62 > 1.7 => ionic SO2: 0.86 < 1.7 => molecular OF2: 0.54 < 1.7 => molecular TiO2: 1.90 > 1.7 => ionic So, the given oxides can be classified as follows: ZnO: Ionic K2O: Ionic SO2: Molecular OF2: Molecular TiO2: Ionic

Key Concepts

Electronegativity

Electronegativity is a key concept in chemistry and plays a vital role in determining the type of bond between atoms. It refers to an atom's ability to attract and hold onto electrons when it forms a compound. Generally, the higher the electronegativity, the more an element wants to "hog" the electrons.

Here's how it works in simple terms:

• Each element has a specific electronegativity value, which can be found in the periodic table.
• In a chemical bond, the atom with higher electronegativity will pull more electron density toward itself.
• The difference in electronegativity values between two bonding atoms determines the bond character.

The difference in electronegativity can tell us a lot about the nature of a bond:

• When the difference is large (greater than 1.7), the bond is usually ionic. This means one atom has essentially taken an electron from the other.
• If the difference is small, the bond is covalent or molecular. The electrons are shared more equally between the atoms.

Understanding how electronegativity works helps us predict and explain the bonding in compounds like oxides.

Periodic Table

The periodic table is an organized chart of elements and is a crucial tool for chemists. It can tell you about an element's properties and help you predict how it might react with others. Each element in the periodic table has a unique place based on its atomic number, and its position can give clues about its chemical behavior.

Here is how the periodic table aids in understanding chemical compounds:

• Elements are arranged in order of increasing atomic number (number of protons).
• Metals are found on the left and middle, while nonmetals are on the right.
• The table is divided into groups (vertical columns) and periods (horizontal rows) with similar properties.

For instance, in the oxides problem:

• Zn (zinc), K (potassium), and Ti (titanium) are metals. They tend to lose electrons easily.
• O (oxygen), S (sulfur), and F (fluorine) are nonmetals and typically gain electrons.

Being familiar with the periodic table helps us expect which elements might form certain types of compounds—ionic or molecular—based on their positions and typical electronegativities.

Oxide Classification

Oxide classification is important in chemistry, as it helps in understanding the properties and behavior of compounds formed with oxygen. Oxides can generally be categorized into two main types: ionic oxides and molecular (also known as covalent) oxides.

**Ionic vs Molecular Oxides:**

• **Ionic oxides** are formed when oxygen binds with metals. They typically of metals with low electronegativities bonding with oxygen, leading to a significant electron transfer.
• **Molecular oxides** form when oxygen pairs with nonmetals, which often results in the sharing of electrons.

Classifying oxides involves considering the electronegativity difference between the oxygen and the other element involved:

• If the electronegativity difference is more than 1.7, the oxide is often ionic, like in ZnO, K extsubscript{2}O, or TiO extsubscript{2}.
• If the difference is less, the oxide is molecular, such as in SO extsubscript{2} and OF extsubscript{2}.

Recognizing whether an oxide is ionic or molecular helps predict other properties such as melting and boiling points, solubility, and more.