Atomic Theory

Who first used the term “atomos,” meaning “uncuttable”?

• A. John Dalton

• B. Democritus

• C. Niels Bohr

• D. J.J. Thomson

What is an atom in modern terms?

• A. The smallest part of a molecule

• B. The smallest particle that still can be considered an element

• C. A particle made only of electrons

• D. A form of pure energy

Why do scientists use models to study atoms?

• A. Atoms are too heavy to move

• B. Atoms are too small to be seen directly

• C. Atoms can be created in labs

• D. Atoms are too bright to look at

According to Dalton’s atomic theory, atoms…

• A. Can be divided into smaller parts

• B. Cannot be created or destroyed

• C. Are made of empty space

• D. Contain only electrons

Before Thomson’s discovery, what did Dalton’s model describe atoms as?

• A. Tiny, indivisible, solid spheres

• B. Positively charged pudding

• C. Nucleus with orbiting electrons

• D. Mostly empty space

In Thomson’s cathode ray experiment, what happened when an electric field was applied?

• A. The ray bent toward the positively charged plate

• B. The ray split into two beams

• C. The ray bent toward the negative plate

• D. The ray was unaffected

What did Thomson conclude from his experiments?

• A. Atoms are indivisible

• B. Atoms contain negatively charged particles

• C. Atoms have a dense nucleus

• D. Atoms are mostly empty space

Thomson proposed the “plum pudding” model. What did it show?

• A. Electrons in fixed orbits

• B. Electrons scattered in a sphere of positive charge

• C. Protons and neutrons together

• D. A tiny dense center

Why did Thomson use different metals for his cathode?

• A. To see which produced the strongest ray

• B. To show that electrons are found in all atoms

• C. To find metals with no rays

• D. To increase the ray’s speed

In the plum pudding model, why is the atom neutral?

• A. Positive sphere balances negative electrons

• B. Protons equal electrons in number

• C. Positive and negative particles orbit each other

• D. Positive center cancels outer electrons