Questions: What Is an Atom?

Question 1

What is the smallest particle of an element that still has the properties of that element?

• A. A molecule
• B. An atom
• C. An electron
• D. A cell

Answer: (B)

An atom is the smallest unit of an element that retains the chemical identity of that element. Molecules are made of atoms bonded together, electrons are subatomic particles inside atoms, and cells are biological structures made of many molecules.

Question 2

Atoms are the smallest things that exist in nature.

• T. True
• F. False

Answer: False

Atoms are made of even smaller subatomic particles — protons, neutrons, and electrons. However, atoms are the smallest unit that still has the chemical properties of a particular element.

Question 3

Why can't you see individual atoms with a regular optical microscope?

Model answer: Atoms are far too small — they are smaller than the wavelengths of visible light, so optical microscopes cannot resolve them.

Visible light has wavelengths hundreds of times larger than an atom. Since optical microscopes work by focusing light, they cannot produce images of objects smaller than those wavelengths. Specialized instruments like electron microscopes or scanning tunneling microscopes use different methods to image atoms.