A piece of sodium metal can be described as
A. a pure substance and a compound.
B. an impure substance that is reactive.
C. an impure substance that is unreactive.
D. a pure substance and an element.
The Correct Answer and Explanation is:
The correct answer is D. a pure substance and an element.
Explanation:
Sodium metal (Na) is a pure substance because it consists of only one type of atom, which is sodium. Pure substances are materials that have a uniform and definite composition. In the case of sodium metal, every particle or atom is identical. It is not mixed with any other substances, so it qualifies as a pure substance.
Furthermore, sodium is classified as an element because it is a chemical substance that cannot be broken down into simpler substances by ordinary chemical means. Elements are the basic building blocks of matter and are found on the periodic table. Sodium is represented by the symbol “Na” and is a metal located in Group 1 (alkali metals) of the periodic table. As an element, sodium has specific physical and chemical properties, such as being a soft, silvery-white metal that is highly reactive, especially with water.
To clarify why the other options are incorrect:
- A. a pure substance and a compound: This is incorrect because a compound is a substance made up of two or more different elements chemically combined. Sodium metal is not a compound but a single element, so it cannot be both a pure substance and a compound.
- B. an impure substance that is reactive: Sodium metal is not impure; it is a pure substance. While it is highly reactive, its reactivity does not change the fact that it is pure.
- C. an impure substance that is unreactive: This option is also incorrect because sodium metal is not impure and is indeed highly reactive, particularly with water, producing heat, hydrogen gas, and a hydroxide.
Thus, the correct description of sodium metal is that it is a pure substance and an element.