Problem 1 - Chemistry The Central Science

Question

For each of these Lewis symbols, indicate the group in the periodic table in which the element \(\mathrm{X}\) belongs: [Section 8.1\(]\) $$(\mathbf{a}) \cdot \dot{\chi} \cdot \quad(\mathbf{b}) \cdot \mathbf{X} \cdot \quad(\mathbf{c}) : \dot{\chi}$$

Step-by-Step Solution

Answer

The elements \(\mathrm{X}\) with given Lewis symbols belong to the following groups in the periodic table: - (a) \(\cdot \dot{\chi} \cdot\) , 2 valence electrons: Group 2 (Alkaline earth metals) - (b) \(\cdot \mathbf{X} \cdot\) , 1 valence electron: Group 1 (Alkali metals) - (c) \(: \dot{\chi}\) , 3 valence electrons: Group 13 (Boron group)

Step 1: Determine the number of valence electrons for each Lewis symbol

A Lewis symbol represents the element with its valence electrons. The number of valence electrons can be determined by counting the number of dots around the element symbol. For each given Lewis symbol, we will count the dots and determine the valence electrons: - (a) \(\cdot \dot{\chi} \cdot\) , there are 2 dots, so 2 valence electrons - (b) \(\cdot \mathbf{X} \cdot\) , there is 1 dot, so 1 valence electron - (c) \(: \dot{\chi}\) , there are 3 dots, so 3 valence electrons

Step 2: Identify the group in the periodic table

The number of valence electrons determines the group in the periodic table to which the element belongs. Here are the groups that correspond to each number of valence electrons: - 1 valence electron: Group 1 (Alkali metals) - 2 valence electrons: Group 2 (Alkaline earth metals) - 3 valence electrons: Group 13 (Boron group) Now, we can assign each element with its number of valence electrons to the appropriate group in the periodic table: - (a) \(\cdot \dot{\chi} \cdot\) , 2 valence electrons: Group 2 (Alkaline earth metals) - (b) \(\cdot \mathbf{X} \cdot\) , 1 valence electron: Group 1 (Alkali metals) - (c) \(: \dot{\chi}\) , 3 valence electrons: Group 13 (Boron group)

Key Concepts

Valence Electrons

Valence electrons are the electrons found in the outermost shell of an atom. They play a critical role in chemical bonding and reactions. Valence electrons are represented in Lewis symbols by dots placed around the chemical symbol of an element. For example, an element represented as "\(\cdot \dot{\chi} \cdot\)" with two dots has two valence electrons. The number of valence electrons helps determine the chemical properties and reactivity of an element.
In general, you can find the number of valence electrons by looking at an element's position in the periodic table. For elements in groups 1 and 2 and groups 13-18, the group number is often the same as the number of valence electrons (with some exceptions in the transition metals). This information is crucial for predicting how elements might interact in chemical reactions.

Periodic Table Groups

Periodic table groups are vertical columns in the periodic table. Each group consists of elements with similar properties and the same number of valence electrons. There are 18 groups in total, with groups 1 and 2 located on the far left, and groups 13 through 18 located on the far right. Elements within the same group often exhibit predictable and similar chemical behavior.
Here's how different groups may typically be defined based on the valence electrons:

• Group 1 has 1 valence electron.
• Group 2 has 2 valence electrons.
• Group 13 has 3 valence electrons.

The concept of periodic table groups is foundational for understanding element classification and chemical reaction predictions.

Alkali Metals

Alkali metals are in Group 1 of the periodic table, and they each have 1 valence electron. This single valence electron is easily lost, making alkali metals highly reactive, especially with water. Elements in this group include lithium (Li), sodium (Na), and potassium (K).
Because of their reactivity, alkali metals are typically stored under oil to prevent them from reacting with moisture in the air. They tend to form +1 ions as they lose their valence electron in reactions. This group shows properties like:

• High reactivity
• Soft texture
• Low density

Understanding alkali metals can help predict their reaction behaviors with other substances.

Alkaline Earth Metals

Alkaline earth metals belong to Group 2 of the periodic table and are characterized by having 2 valence electrons. This makes them less reactive than the alkali metals since they need to lose two electrons instead of one. Examples include magnesium (Mg) and calcium (Ca).
The two valence electrons allow these metals to form +2 ions by losing both electrons during reactions. Properties of alkaline earth metals include:

• Moderate reactivity
• Higher melting points compared to alkali metals
• Forming stable compounds like salts

These sub-reactions are important in various biological and industrial processes, making the understanding of this group fundamental for students.

Boron Group

The Boron group, or Group 13, contains elements with 3 valence electrons. This group includes boron (B), aluminum (Al), and gallium (Ga). Unlike alkali and alkaline earth metals, the elements in the Boron group form +3 oxidation states in reactions by losing their 3 valence electrons.
Boron, the only non-metal in this group, has unique properties compared to its metallic neighbors. Boron compounds are used in a variety of applications like detergents and cosmetics, whereas aluminum is known for its widespread use due to its lightweight and corrosion resistance. Understanding the chemical properties of the Boron group is vital for grasping how these elements interact and contribute to various chemical processes.