State the five points of Dalton’s atomic theory: 1. Atoms are indivisible and indestructible particles. 2. All atoms of the same element are identical in mass and properties. 3. Compounds are formed by a combination of two or more different kinds of atoms. 4. A chemical reaction involves the rearrangement, separation, or combination of atoms. 5. Atoms cannot be created or destroyed in a chemical reaction. Name the scientist/philosopher who found the following conclusions: a. Atom contains a small positive bundle of matter in the center: Ernest Rutherford b. A great philosopher who found that atom is continuous: Aristotle c. Found that electrons are scattered in a pool of positive charge: J.J. Thomson Identify the following experiment: Discharge Tube Air at very low pressure Anode Cathode Cathode rays To Vacuum Pump High Voltage Generator
The Correct Answer and Explanation is:
Correct Answer:
Dalton’s Atomic Theory – Five Main Points:
- Atoms are indivisible and indestructible particles.
- All atoms of the same element are identical in mass and properties.
- Compounds are formed by a combination of two or more different kinds of atoms.
- A chemical reaction involves the rearrangement, separation, or combination of atoms.
- Atoms cannot be created or destroyed in a chemical reaction.
Scientists/Philosophers and Their Discoveries:
a. Atom contains a small positive bundle of matter in the center – Ernest Rutherford
b. A great philosopher who found that atom is continuous – Aristotle
c. Found that electrons are scattered in a pool of positive charge – J.J. Thomson
Experiment Identified:
The described experiment is J.J. Thomson’s Cathode Ray Tube Experiment.
300-Word Textbook-Style Explanation:
Dalton’s atomic theory, proposed in the early 1800s by John Dalton, laid the foundation for modern chemistry. He introduced the idea that all matter is composed of atoms—tiny, indivisible, and indestructible particles. He stated that atoms of the same element are identical in mass and properties, and that compounds are formed when atoms of different elements combine in fixed ratios. Dalton also proposed that during chemical reactions, atoms are simply rearranged, not destroyed or created.
Later developments in atomic structure came through groundbreaking experiments. Ernest Rutherford, through his famous gold foil experiment, concluded that the atom consists of a dense central core, the nucleus, which is positively charged. This overturned the earlier “plum pudding” model proposed by J.J. Thomson, who believed that electrons were scattered within a positively charged “soup.”
J.J. Thomson had discovered electrons using a discharge tube, an apparatus where high voltage was applied across electrodes in a tube containing gas at low pressure. He observed a stream of negatively charged particles (later called electrons) moving from the cathode to the anode. These rays, called cathode rays, were deflected by electric and magnetic fields, proving they had mass and charge. This led to the discovery of the electron and the formulation of the first subatomic model.
On the other hand, Aristotle, a Greek philosopher, believed that matter was continuous and could be divided endlessly. He rejected the idea of atoms, which had been earlier proposed by Democritus. While his views were later disproven, they influenced scientific thought for many centuries.
Together, these contributions mark the evolution of our understanding of atomic structure.
