Federal Emergency Management Agency (FEMA) Standardized Awareness Practice Test

What defines an atom?

1. The smallest particle of a compound

2. The smallest particle that can exist alone or in combination

3. A subatomic particle with no charge

4. A particle exclusively found in metals

The correct answer is: The smallest particle that can exist alone or in combination

An atom is defined as the smallest particle that can exist alone or in combination, making this choice accurate. Atoms are the basic building blocks of matter and can exist independently or bond with other atoms to form molecules and compounds. Each atom consists of a nucleus made up of protons and neutrons, surrounded by electrons that orbit the nucleus. This ability to exist independently or bond with others highlights the fundamental nature of atoms in forming all matter. Other choices do not provide the complete definition of an atom. Describing it as the smallest particle of a compound neglects the fact that atoms can exist independently. The option regarding a subatomic particle with no charge points to neutrons, which are indeed part of an atom but do not define what an atom is. Finally, stating that a particle is exclusively found in metals is misleading, as atoms are not limited to metals; they are found in all types of matter, including non-metals and compounds. Thus, the definition that emphasizes the independent existence and combinatory nature of atoms is both comprehensive and correct.