Question

Use the periodic table of the elements, located on the inside back cover, to classify the following substances as elements or compounds: iron, aluminum, carbon dioxide, gold, water, and sugar.

Short answer

Iron, aluminum, and gold are elements; carbon dioxide, water, and sugar are compounds.

Step-by-step solution

Understand What Elements and Compounds Are

An element is a substance that consists of only one type of atom and cannot be broken down into a simpler substance. On the other hand, a compound is a substance formed when two or more different types of atoms bond together.

Identify Elements

Review the list of substances: iron, aluminum, carbon dioxide, gold, water, and sugar. Based on the definitions, identify which substances are elements. Both iron (Fe), aluminum (Al), and gold (Au) appear as single items on the periodic table, confirming they are elements.

Identify Compounds

Now, look at the remaining substances: carbon dioxide, water, and sugar. As compounds are formed from two or more elements, carbon dioxide ( CO_2 ), water ( H_2O ), and sugar ( C_6H_{12}O_6 ) are all compounds because their chemical formulas indicate they consist of more than one element.

Key concepts

Elements

Elements are pure substances that consist solely of one type of atom. Each element retains its unique properties and cannot be broken down into anything simpler by chemical means. An everyday example of an element is iron. Iron, with the chemical symbol Fe, is made entirely of iron atoms. This is why it's found as a single entry on the periodic table. Elements are like the fundamental building blocks in chemistry. When you find a single type of atom lined up in nature or a scientific setting, you're looking at an element.

To identify an element, consider whether the substance can be found on the periodic table. If it is present as a single entry, then it is classified as an element.

Periodic Table

The periodic table is a comprehensive chart that organizes all known chemical elements based on their atomic number, electron configurations, and recurring chemical properties. It is a vital tool for chemists and students alike, allowing easy reference and comparison among elements.

Atoms in the periodic table are arranged in rows and columns, known as periods and groups. This layout highlights trends in behavior and similarities between the elements. For example, elements in the same group often share similar chemical properties.

Whether you are identifying a substance as an element or studying properties like reactivity, the periodic table provides essential insights and serves as a roadmap for exploring chemical behavior.

Chemical Formulas

Chemical formulas represent the types and numbers of atoms in a molecule. They are a shorthand way of expressing the composition of chemical compounds. For instance, the chemical formula for water, \( H_2O \), tells us each molecule consists of two hydrogen atoms and one oxygen atom.

By examining a chemical formula, we can determine whether a substance is an element or a compound. Elements have simple chemical symbols like \( ext{Al} \) for aluminum, while compounds have more complex formulas like \( ext{CO}_2 \) for carbon dioxide.

• Formulas are concise, making it easier to convey information about substances.
• They help to easily differentiate elements (single letter/symbol) from compounds (combination of letters).

Bonding of Atoms

Atoms bond together to form compounds, which is a central idea in chemistry. This process is driven by the attraction between the atoms’ electrons and nuclei, seeking stability through balanced energy configurations.

Bonds can be covalent, where atoms share electrons, as in water \( H_2O \), or ionic, where electrons are transferred, resulting in charged particles, such as in table salt \( NaCl \).

The type and strength of bonding determine the properties of the compound, such as melting point, solubility, and conductivity. Understanding these bonds is crucial because they dictate how substances interact chemically. Therefore, chemistry would not be the same without understanding the bonding of atoms.