Problem 33 - Chemistry The Science in Context

Question

Draw the Lewis symbol of an ion that has the following: a. \(1+\) charge and 1 valence electron b. \(3+\) charge and 0 valence electrons

Step-by-Step Solution

Answer

Question: Create the Lewis symbols for two ions based on their charges and valence electrons. One ion has a charge of 1+ and 1 valence electron, while the other has a charge of 3+ and 0 valence electrons. Answer: The Lewis symbols for the ions are: a. \(\overset{+}{\underset{1}{\text{Be}}}\) for a \(1+\) charged ion with 1 valence electron b. \(\overset{3+}{\text{Al}}\) for a \(3+\) charged ion with 0 valence electrons

Step 1: Determine the number of valence electrons for each ion

To determine the Lewis symbol, we first need to know the number of valence electrons for each ion. For each ion, we can calculate the number of valence electrons by considering its charge. a. An ion with a \(1+\) charge and 1 valence electron must have lost 1 electron, which is equivalent to an element that originally had 2 valence electrons. b. An ion with a \(3+\) charge and 0 valence electrons must have lost 3 electrons, which is equivalent to an element that originally had 3 valence electrons.

Step 2: Identify the elements corresponding to the valence electrons

Now, we can identify the elements that correspond to the calculated valence electrons: a. An element with 2 valence electrons is found in Group 2 of the periodic table, which includes elements like Beryllium (Be) and Magnesium (Mg). b. An element with 3 valence electrons is found in Group 13 of the periodic table, which includes elements like Boron (B) and Aluminium (Al).

Step 3: Draw the Lewis symbols for the ions

Finally, we can draw the Lewis symbol for each ion by removing the respective number of valence electrons according to their charge. a. Let's draw the Lewis symbol for a Group 2 element (e.g., Be) and remove 1 electron, resulting in a \(1+\) charge: \(\overset{+}{\underset{1}{\text{Be}}}\) Note that there are no dots (valence electrons) surrounding the Be atom, as the ion has only one valence electron, which was removed due to the positive charge. b. Let's draw the Lewis symbol for a Group 13 element (e.g., Al) and remove 3 electrons, resulting in a \(3+\) charge: \(\overset{3+}{\text{Al}}\) Again, there are no dots (valence electrons) surrounding the Al atom, as the ion lost all its valence electrons due to the positive charge. In conclusion, the Lewis symbols for the ions are: a. \(\overset{+}{\underset{1}{\text{Be}}}\) for a \(1+\) charged ion with 1 valence electron b. \(\overset{3+}{\text{Al}}\) for a \(3+\) charged ion with 0 valence electrons

Key Concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom. They are crucial because they participate in chemical bonding. The number of valence electrons determines how an element reacts with other substances. For instance, the Group 1 elements (alkali metals) have 1 valence electron. This makes them highly reactive, as they tend to lose that single electron to achieve a stable noble gas configuration.

• They dictate the chemical properties of an element.
• Their number influences the formation of ions.
• They are responsible for the bonding behavior of elements.

An element's location on the periodic table can often tell you the number of its valence electrons. As you move from left to right across a period, the number of valence electrons increases. Understanding this helps in predicting the types of ions an element might form. For example, Magnesium (Mg) with 2 valence electrons (found in Group 2) tends to form a 2+ ion by losing both electrons.

Positive Charge Ions

Ions are atoms that have lost or gained electrons, resulting in a charge. When an atom loses one or more electrons, it becomes positively charged. These are known as cations.

• Cations form when metals lose valence electrons.
• The positive charge indicates how many electrons were lost.
• The formation of cations is driven by the desire for a full outer electronic shell.

For instance, when Calcium (Ca) in Group 2 loses 2 electrons, it forms a 2+ ion. This process results in a stable electronic arrangement similar to that of the noble gases. The positive charge on the ion is essential because it affects how the ion interacts with other ions and molecules. In chemical reactions, positive ions often pair with negative ions (anions) to form stable compounds like salts.

Periodic Table Groups

The periodic table is structured into groups and periods. A group is a vertical column and typically contains elements with similar chemical properties. This similarity arises because elements in the same group have the same number of valence electrons.

• Group 1: Alkali metals with 1 valence electron.
• Group 2: Alkaline earth metals with 2 valence electrons.
• Group 13: Elements with 3 valence electrons.

These are just a few examples, but this pattern holds true throughout the periodic table. For instance, Beryllium (Be) and Magnesium (Mg), both in Group 2, are known for forming compounds like oxides and halides by losing their valence electrons. Similarly, elements in Group 13, like Boron (B) and Aluminum (Al), form compounds by losing their three valence electrons, which can result in cations with a 3+ charge. Hence, the periodic table is an invaluable tool for understanding elemental behavior and predicting chemical reactions.