The document discusses the development of atomic models from ancient Greek philosophers to modern scientific theories. It describes early ideas that matter was made of tiny indivisible particles called atoms. John Dalton proposed the first modern atomic theory in the 1800s, modeling atoms as hard spheres. J.J. Thomson's experiments showed atoms contain negatively charged electrons. Ernest Rutherford's experiments revealed atoms have a small, dense nucleus containing positive charge. Neutrons were later discovered in atomic nuclei. Modern atomic theory pictures electrons in electron clouds surrounding atomic nuclei.

1. Chapter 11: Atoms, Elements, Compounds, and Mixtures Table of Contents Section 3: Compounds and Mixtures Section 1: Models of the Atom Section 2: The Simplest Matter

35. 1 Section Check Question 1 Explain why early Greek philosophers thought that matter was composed of atoms. NC: 1.05

36. 1 Section Check Answer The early Greeks didn’t do experiments; they relied only on reasoning. They reasoned that if you kept cutting something in half, eventually you would have a piece so small it couldn’t be cut any more. NC: 1.05

37. 1 Section Check Question 2 The first modern atomic theory was proposed by _______. A. Aristotle B. Dalton C. Rutherford D. Thompson NC: 4.03

38. 1 Section Check Answer The answer is B. John Dalton was a 19th century English school teacher. He thought atoms were tiny, hard spheres. NC: 4.03

39. 1 Section Check Question 2 A cathode-ray tube has two electrodes, one at either end. These are known as the _______ and the _______. NC: 1.07

40. 1 Section Check Answer The answer is cathode and anode. Sometimes a cathode-ray tube is abbreviated to CRT. NC: 1.07