Question 1: Define an atom in your own words.

Answer: An atom is the smallest unit of matter that retains the chemical properties of an element.

Question 2: Who proposed the first modern atomic theory and what was its main idea?

Answer: John Dalton proposed the first modern atomic theory, stating that all matter is made up of indivisible atoms, and atoms of the same element are identical.

Question 3: Explain the significance of J.J. Thomson's discovery related to the atom.

Answer: J.J. Thomson discovered the electron, showing that atoms are divisible and contain smaller particles.

Question 4: Describe Rutherford's gold foil experiment and its conclusion about atomic structure.

Answer: Rutherford's gold foil experiment involved firing alpha particles at a thin gold sheet. Most particles passed through, but some deflected sharply, leading to the conclusion that an atom has a small, dense, positively charged nucleus at its center.

Question 5: Multiple Choice: Which model of the atom introduced the idea of electrons orbiting the nucleus in specific energy levels?

Answer: Bohr Model

Question 6: Fill in the blank: The atomic model that describes electrons as existing in probabilistic regions around the nucleus is called the __________ model.

Answer: Quantum Mechanical

Question 7: Identify two contributions of Marie Curie to atomic science.

Answer: Marie Curie discovered radioactivity and isolated elements like radium and polonium.

Question 8: Calculate the number of neutrons in an atom of carbon-14. (Atomic number of carbon = 6)

Answer: 8

Question 9: Describe a simple experiment to demonstrate the presence of electrons in an atom (theory only).

Answer: A possible experiment is to pass an electric current through a gas at low pressure and observe the glow discharge, indicating the presence of charged particles (electrons) within the gas.

Question 10: Explain how the discovery of the neutron influenced atomic models.

Answer: The discovery of the neutron explained the existence of isotopes and helped refine models of the nucleus by accounting for additional mass without charge.

Question 11: In your opinion, which scientist's contribution was most crucial in shaping our current understanding of the atom? Justify your answer.

Answer: Answers may vary; students should justify their choice by referencing contributions such as Rutherford's discovery of the nucleus, Bohr's quantized energy levels, or Schrödinger's quantum model, explaining how each advanced atomic understanding.