SECOND QUARTER EXAMINATION IN SCIENCE 8 S.Y: 2025-2026

Which of the following shows the correct order of Atomic Theory Timeline?

• A. Dalton, Thomson, Rutherford, Modern, Democritus Thomson
• B. Democritus, Dalton, Thomson, Rutherford, Modern
• C. Modern, Democritus, Thomson, Rutherford, Dalton
• D. Rutherford, Modern, Dalton, Democritus

Which conclusion BEST reflects J.J. Thomson's cathode ray experiment in shaping atomic theory discovery about the nature of atoms?

• A. Atoms are neutral and cannot be broken down into smaller parts.
• B. Atoms consist mostly of empty space, with mass concentrated in a dense core.
• C. Atoms contain subatomic particles, including tiny negatively charged electrons.
• D. Atoms are composed entirely of electromagnetic energy and have no physical structure.

Which of the following statements BEST illustrates the Law of Definite Proportions?

• A. The mass ratio of hydrogen to oxygen in water (H₂O) varies depending on its source.
• B. The mass of carbon in carbon dioxide is always 3 times the mass of oxygen, regardless of the source.
• C. The mass of oxygen in water is always 8 times the mass of hydrogen, regardless of the source.
• D. The mass ratio of carbon to oxygen in CO₂ differs between CO₂ from fossil fuels and CO₂ from respiration.

During a science exhibition, a student presents a timeline of atomic models. She includes Dalton, Thomson, Rutherford, and Bohr. What key idea did Dalton contribute?

• A. Atoms have a nucleus surrounded by electrons.
• B. Atoms are made of smaller particles.
• C. Atoms are solid spheres that cannot be divided.
• D. Electrons orbit the nucleus in specific paths.

Which of the following statements did NOT correctly describe the results of the experiments done to determine the nature of the atom?

• A. The cathode ray tube proved that electrons are negatively charged particles
• B. Rutherford’s thin gold foil experiment led to the discovery of the charge of the nucleus.
• C. The results of Rutherford’s experiment supported J.J. Thomson’s plum pudding model.
• D. Millikan’s oil drop experiment showed that the charge of the electron is -1.6022 x 10-19 C.

If Rutherford’s experiment proved the correctness of J.J. Thomson’s model, what would he observe?

• A. Alpha particles are greatly deflected by the foil.
• B. Alpha particles bounced back from the foil.
• C. Alpha particles had little to no deflection.
• D. More alpha particles are formed.

Which scientist proposed that the atom looked like the image below?

• A. Ernest Rutherford
• B. JJ Thomson
• C. John Dalton
• D. Niels Bohr

Which of the following statements about the Quantum Mechanical Model of the atom is TRUE?

• A. Electrons orbit the nucleus in fixed paths.
• B. Atoms are indivisible according to this model.
• C. The atomic nucleus is composed of only protons.
• D. Electrons exist in defined energy levels and are described by probabilities.

A teacher uses a diagram showing a small dense center and circular layers around it. What do the circular layers most likely represent?

• A. Atomic orbitals
• B. Electron shells
• C. Neutrons
• D. Protons

If an atom has 12 positively charged subatomic particles, which of the following must it also have to be considered a neutral atom?

• A. 12 neutrons
• B. 12 electrons
• C. 12 protons
• D. 24 protons and neutrons