Question

Classify each of the following as an element, compound, or mixture: (a) sodium metal (b) chlorine gas (c) sodium chloride (d) salt water

Short answer

(a) Element, (b) Element, (c) Compound, (d) Mixture.

Step-by-step solution

Classify Sodium Metal

Sodium is a pure chemical substance that contains only one type of atom. It is found on the periodic table and is represented by the symbol Na. Since it consists of only one kind of element, sodium metal is classified as an **element**.

Classify Chlorine Gas

Chlorine gas consists solely of chlorine molecules, each containing two chlorine atoms. As it contains only chlorine, which is a pure chemical element found on the periodic table represented by the symbol Cl, chlorine gas is classified as an **element**.

Classify Sodium Chloride

Sodium chloride, commonly known as table salt, is a chemical compound made by the chemical combination of the two elements sodium (Na) and chlorine (Cl). Since it is composed of more than one type of element in a definite ratio, sodium chloride is classified as a **compound**.

Classify Salt Water

Salt water is a homogeneous mixture made by dissolving sodium chloride (salt) in water. It consists of two different substances mixed together physically, but not chemically bonded, which makes it a **mixture**.

Key concepts

Mixtures

Mixtures are fascinating in the world of chemistry because they are combinations of two or more substances where each retains its original properties. Unlike compounds where the substances combine chemically, mixtures simply blend together physically. This means that the components in a mixture can be easily separated using physical methods like filtration or evaporation.
For instance, **salt water** is a perfect example of a mixture. Here, the salt (sodium chloride) is dissolved in water, but both substances maintain their own unique properties. You can observe this distinction if you were to evaporate the water, leaving the salt behind. Hence, salt water is classified as a homogeneous mixture because it is uniform throughout, unlike a heterogeneous mixture where you can see the different components.

• Mixtures consist of two or more substances.
• Components can be separated physically.
• Components keep their original properties.

Understanding mixtures helps in differentiating them from compounds and elements, providing a clearer view of chemical classification.

Chemical Classification

Chemical classification is a systematic way to organize substances based on their chemical properties and composition. The classification helps in deciding whether a substance is an element, compound, or mixture.
A **element** is a basic substance that cannot be broken down into simpler substances through chemical means. Elements are composed of only one type of atom. For example, sodium (Na) and chlorine (Cl) are elements because they consist of single types of atoms.
On the other hand, a **compound** is a substance formed when two or more elements chemically combine in a fixed ratio. This results in new properties. Sodium chloride (NaCl), commonly referred to as table salt, is a compound because it comprises sodium and chlorine bonded in a specific 1:1 ratio.
Elements and compounds have distinct characteristics that are beneficial in identifying their roles in various chemical reactions and processes. Recognizing these differences is key to understanding the complexities of the molecular world.

• Elements are made of one kind of atom, found on the periodic table.
• Compounds consist of two or more elements combined chemically.
• Mixtures are physical combinations of substances, keeping original properties.

Periodic Table

The periodic table is an organized chart that displays all known chemical elements based on their properties. It serves as an essential tool in chemical classification and helps predict the behavior and characteristics of elements in chemical reactions.
Elements are arranged in order of increasing atomic number (number of protons in the nucleus). The table also groups elements with similar chemical properties into columns, known as families or groups. For instance, sodium (Na) is located in Group 1, which contains elements known as alkali metals that are highly reactive.
The periodic table also categorizes elements into different blocks based on electron configurations, such as s-block, p-block, d-block, and f-block. Each element's position provides insights into its physical and chemical properties, such as melting point, density, and reactivity.

• Arranges elements by increasing atomic number.
• Groups elements with similar properties.
• Helps predict how elements will behave in reactions.

The periodic table is not just a list but a powerful tool that gives a comprehensive overview of elements, helping in the study and understanding of chemistry at a deeper level.