Problem 1 - Chemistry: The Central Science

Question

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

Step-by-Step Solution

Answer

For the given Lewis symbols, the elements belong to the following groups in the periodic table: (a) \(\dot{X}\): Group 1 (alkali metals) (b) \(\mathrm{X}\): Group 18 (noble gases) (c) \(\dot{X}\cdot\): Group 13 (boron group).

Step 1: (a) Step 1: Identify the number of valence electrons

For the first Lewis symbol given as \(\dot{X}\), there is one dot around the symbol representing one valence electron.

Step 2: (a) Step 2: Determine the element's group

Since there is only one valence electron, the element belongs to Group 1 of the periodic table (the alkali metals).

Step 3: (b) Step 1: Identify the number of valence electrons

For the second Lewis symbol given as \(\mathrm{X}\), there are no dots around the symbol, which means the element has no valence electrons.

Step 4: (b) Step 2: Determine the element's group

Since the element has no valence electrons, it belongs to Group 18 of the periodic table (the noble gases).

Step 5: (c) Step 1: Identify the number of valence electrons

For the third Lewis symbol given as \(\dot{X}\cdot\), there is one dot and one pair of electrons, indicating a total of three valence electrons.

Step 6: (c) Step 2: Determine the element's group

Since there are three valence electrons, the element belongs to Group 13 of the periodic table (the boron group).

Key Concepts

Valence Electrons

Valence electrons are the electrons located in the outermost shell of an atom. They play a crucial role in chemical bonding and determine the reactivity of an element. The number of valence electrons influences how an element will interact with others, often dictating whether they will gain, lose, or share electrons to achieve a stable electron arrangement. In the context of Lewis structures, valence electrons are represented by dots around the elemental symbol. For example:

• An element with one dot like \( \dot{X} \) has 1 valence electron.
• More dots indicate more valence electrons, such as \( :X:\) implies 4 valence electrons.

This simple representation helps easily identify how elements are likely to bond in molecules or compounds.

Periodic Table Groups

The periodic table is arranged in such a way that elements are grouped together based on similar properties. These groups are columns that run from top to bottom on the table and are numbered 1 through 18. Each group contains elements that possess the same number of valence electrons, which results in similarities in chemical behavior. For example, all elements in Group 1 have 1 valence electron, making them highly reactive. Understanding these groups helps in predicting the chemical properties of unknown elements, enabling a deeper insight into their potential reactions and interactions with other substances.

Alkali Metals

Alkali metals belong to Group 1 of the periodic table and are known for their high reactivity. This group consists of lithium, sodium, potassium, rubidium, cesium, and francium. Each of these elements has just one valence electron in their outermost shell, making them eager to lose that single electron to form a stable, positive ion. The characteristic properties of alkali metals include:

• High reactivity with water and air.
• Soft texture and low melting points.
• Tendency to form ionic compounds, especially with halogens.

These elements are rarely found in their pure state in nature due to their reactive nature.

Noble Gases

Noble gases are found in Group 18 of the periodic table. These elements, which include helium, neon, argon, krypton, xenon, and radon, are known for their very low chemical reactivity. Part of their stability comes from having a complete set of valence electrons, either 2 or 8, which makes their electron configuration particularly stable. Due to their full valence shell, noble gases typically do not form compounds easily. Some of their notable features include:

• Being colorless, odorless, and tasteless.
• Nonflammablity.
• Used in lighting, welding, and space technologies due to their inert nature.

Their unique characteristics make them quite special compared to other elements on the periodic table.

Boron Group

The boron group, also known as Group 13, consists of elements which include boron, aluminum, gallium, indium, and thallium. Elements in this group typically have three valence electrons. They exhibit a mix of metallic and non-metallic properties, making them quite versatile in nature. Some highlights of the boron group:

• Boron is a metalloid, exhibiting properties of both metals and non-metals.
• Aluminum is a widely used metal due to its lightweight and corrosion-resistant properties.
• Gallium and indium are used in electronics, particularly in semiconductor technology.

Understanding the boron group helps predict the behavior of these elements in various chemical reactions and applications.