Final answer:
Dalton's atomic theory teaches that atoms are the smallest indivisible units of matter, identical within an element but different across elements, which combine in fixed ratios to form compounds, and are neither created nor destroyed in chemical reactions, adhering to the law of conservation of matter. Later discoveries introduced the concepts of subatomic particles, isotopes, and nuclear reactions. The choice will be C. The smallest unit of matter is the atom.
Step-by-step explanation:
John Dalton's atomic theory, proposed in the early 19th century, provides the foundation of our understanding of chemical science. According to his theory:
- All matter is composed of extremely small particles called atoms.
- Atoms cannot be subdivided, created, or destroyed.
- Atoms of a given element are identical in size, mass, and other properties, while atoms of different elements differ in these attributes.
- Atoms of different elements can combine in whole number ratios to form chemical compounds.
- In chemical reactions, atoms are rearranged, combined, or separated, but the total mass remains constant (law of conservation of matter).
Although Dalton's theory has been revised with the discovery that atoms can be subdivided into smaller particles (protons, neutrons, and electrons), that atoms of the same element can have different masses (isotopes), and that atoms can be transformed into other atoms through nuclear reactions, the core ideas remain crucial to our understanding of matter.