Question

Refer to the periodic table and classify each of the following elements as a metal, nonmetal, or semimetal: (a) \(\mathrm{H}\) (b) He (c) Hf (d) Ho

Short answer

(a) Nonmetal, (b) Nonmetal, (c) Metal, (d) Metal.

Step-by-step solution

Understand the Elements

First, identify the elements given: (a) \( \text{H (Hydrogen)} \), (b) \( \text{He (Helium)} \), (c) \( \text{Hf (Hafnium)} \), and (d) \( \text{Ho (Holmium)} \). These elements will need to be classified as either a metal, nonmetal, or semimetal.

Locate on the Periodic Table

Find each element on the periodic table. The periodic table is divided into metals, nonmetals, and semimetals, which are also known as metalloids. This will help determine the classification.

Classify Hydrogen

Hydrogen (\( \text{H} \)) is located in Group 1 of the periodic table. Despite being positioned with the alkali metals, \( \text{H} \) is a nonmetal.

Classify Helium

Helium (\( \text{He} \)) is located in Group 18 and is a noble gas. All noble gases are nonmetals.

Classify Hafnium

Hafnium (\( \text{Hf} \)) is in the transition metals section of the periodic table, typically found in Group 4. Therefore, \( \text{Hf} \) is classified as a metal.

Classify Holmium

Holmium (\( \text{Ho} \)) is part of the lanthanide series, which are commonly known as rare earth metals. Therefore, \( \text{Ho} \) is classified as a metal.

Key concepts

Element Classification

Element classification is a fundamental concept when studying chemistry and the periodic table. Understanding it helps us comprehend how elements behave and interact with each other. Elements on the periodic table are categorized based on their physical and chemical properties into three main groups: metals, nonmetals, and semimetals (often called metalloids). This classification helps chemists predict how an element will react, what kinds of bonds it might form, and its general state in different environments.

Element classification is crucial for:

• Predicting chemical reactions and properties.
• Determining an element's role in various scientific and industrial processes.
• Understanding trends in element behavior across the periodic table.

Look at where an element is placed on the periodic table to make these predictions. Its group, period, and position provide hints about its classification.

Metals

Metals are one of the largest categories of elements on the periodic table. They are primarily found on the left side and in the center of the table. Metals are known for their shiny appearance and are good conductors of heat and electricity. They are also malleable, which means they can be hammered into thin sheets, and ductile, allowing them to be drawn into wires.

Characteristics of metals include:

• High conductivity of heat and electricity.
• Malleable and ductile nature.
• Usually have high melting and boiling points.
• Tend to lose electrons during chemical reactions.

Common examples include iron ( Fe ), copper ( Cu ), and gold ( Au ). In the exercise above, both hafnium ( Hf ) and holmium ( Ho ) are classified as metals due to their placement and typical properties of metals.

Nonmetals

Nonmetals have distinct properties compared to metals, often located on the right side of the periodic table. They generally exhibit opposite traits to those of metals. Nonmetals have more varied physical properties, with some existing as gases at room temperature while others are solids.

Key features of nonmetals include:

• Poor conductors of heat and electricity.
• Not shiny, usually dull in appearance.
• Brittle when solid, not malleable or ductile.
• Tend to gain electrons in reactions to form negative ions.

Common nonmetals include oxygen ( O ), carbon ( C ), and nitrogen ( N ). In the given exercise, hydrogen ( H ) and helium ( He ) fall under the nonmetal category based on their properties and position on the periodic table.

Semimetals

Semimetals, or metalloids, possess characteristics that are intermediate between metals and nonmetals. This gives them unique properties making them useful in various applications, especially in electronics. They are typically found between the metals and nonmetals on the periodic table and are known for having properties that allow them to conduct electricity better than nonmetals but not as well as metals. Some important traits of semimetals include:

• Poorer conductors than metals, but better than nonmetals.
• Can behave as either electrical conductors or insulators.
• Often used in semiconductor technology.

Examples of semimetals include silicon ( Si ), boron ( B ), and germanium ( Ge ). These elements are crucial in the tech industry, particularly in the production of computer chips and transistors.