Humber Admissions Practice Test

What is an element?

1. A molecule composed of various kinds of atoms

2. A simple unit that cannot be broken down by chemical reactions

3. A compound of several different atoms

4. A type of isotope

The correct answer is: A simple unit that cannot be broken down by chemical reactions

An element is defined as a fundamental substance that cannot be broken down into simpler substances by chemical reactions. Each element consists of atoms that share the same number of protons, which determines their position on the periodic table and their unique properties. Since elements are the building blocks of matter, they are pure substances that can exist in various forms, such as gases, liquids, or solids, but fundamentally remain unchanged at the atomic level. In contrast, a molecule composed of various kinds of atoms refers to a compound, which is different from an element as it combines multiple elements into one substance. Similarly, a compound of several different atoms also indicates a combination of elements rather than a single pure substance. A type of isotope involves variations of an element based on the number of neutrons in its atomic structure, but this does not change the fundamental definition of what constitutes an element. Therefore, the definition aligns accurately with the answer provided, highlighting the importance of understanding elements as the purest forms of matter in the context of chemistry.