Problem 4 - Chemistry Matter and Change

Question

Identify each of the following as a representative element or a transition element. a. lithium (Li) b. platinum (Pt) c. promethium (Pm) d. carbon (C)

Step-by-Step Solution

Answer

a. Lithium (Li) - Representative element b. Platinum (Pt) - Transition element c. Promethium (Pm) - Transition element (Lanthanides series) d. Carbon (C) - Representative element

Step 1: Locate the elements on the periodic table

Check the periodic table for the group and period numbers of each element to categorize them as either representative or transition elements.

Step 2: Identify the type of each element

a. Lithium (Li): Lithium is in Group 1 of the periodic table, which means it is a representative element. b. Platinum (Pt): Platinum is found in Group 10, which is part of the transition elements group. c. Promethium (Pm): Promethium is in the f-block, specifically in the Lanthanides series, which makes it a rare earth element - not a representative or transition element. However, for the sake of simplicity, we can consider it as a transition element given its general characteristics. d. Carbon (C): Carbon belongs to Group 14 of the periodic table, making it a representative element.

Step 3: Summarize the results

a. Lithium (Li) - Representative element b. Platinum (Pt) - Transition element c. Promethium (Pm) - Transition element (Lanthanides series) d. Carbon (C) - Representative element

Key Concepts

Representative Elements

Representative elements, also known as the main group elements, are found in the s and p blocks of the periodic table. These elements include those in Groups 1, 2, and 13 to 18. They are characterized by their predictable chemical behavior.
They typically form simple ions and are often significant in the formation of compounds. For example:

• Group 1 elements, known as alkali metals, like lithium (Li), form +1 cations and are highly reactive.
• Group 14 elements, such as carbon (C), can form four bonds, making them highly versatile and crucial in organic chemistry.

These elements exhibit a wide range of oxidation states and have varied physical and chemical properties, including metals, nonmetals, and metalloids.

Transition Elements

Transition elements are located in the d-block and are known for their ability to form various oxidation states. They are comprised of Groups 3 to 12 on the periodic table.
These elements, like platinum (Pt), often have high melting points, are good conductors of electricity, and can form complex ions. Key characteristics include:

• Variable Oxidation States: Transition metals can exhibit multiple oxidation states, contributing to their ability to form compounds with various properties.
• Colored Compounds: Due to d-d electron transitions, many transition metal compounds are colored, which makes them useful in dyes and pigments.

Additionally, these elements often have catalytic properties and are essential in processes such as industrial catalysis.

Lanthanides Series

The Lanthanides series, often referred to as rare earth elements, consists of 15 metallic elements from atomic numbers 57 through 71, situated in the f-block of the periodic table. Despite their name, these elements, like promethium (Pm), are relatively abundant in the Earth's crust.
They are known for their similar properties, including their silvery shine and ability to emit light when exposed to electricity or radiation. These elements are unique due to:

• Magnetic Properties: Many lanthanides can exhibit strong magnetic properties and are used in producing powerful magnets.
• Phosphorescence: Lanthanides are valuable in the production of phosphorescent materials for various applications, including TV screens and LED lights.

While not typically categorized strictly as transition elements, they share some characteristics due to their placement in the f-block.

Chemical Elements Identification

Identifying chemical elements involves understanding their placement within the periodic table, which dictates their properties and classification. To identify an element:

• Locate the element's group and period number.
• Determine if it belongs to s, p, d, or f block by its position, which helps in classifying it as a representative or transition element.

For instance:

• Lithium (Li) and Carbon (C) are in the s and p blocks respectively, thus classified as representative elements due to their positions in Groups 1 and 14.
• Platinum (Pt) is found in the d-block, categorizing it as a transition element.
• Promethium (Pm) situates in the f-block and is part of the Lanthanides, making it a rare earth element.

Learning how to read the periodic table is crucial for element identification and understanding their chemical behavior.