Dalton described the atomic nature of matter – is that the end of the story?
Objectives • To learn more about how the understanding of atomic structure developed • To learn about the internal parts of an atom • To understand Rutherford’s experiment • To describe some important features of subatomic particles • To learn about the terms isotope, atomic number, and mass number • To understand the use of the symbol to describe a given atom
A. The Structure of the Atom • Experiments by J.J. Thomson in the 1890’s showed that atoms contain electrons. • Cathode ray tube The Discovery of the Electron Electric Potential = Voltage
A. The Structure of the Atom The Plum Pudding (Chocolate Chip Cookie) Model The Discovery of the Electron
A. The Structure of the Atom Rutherford’s Experiment (1911) α particles are very small and positively charged
A. The Structure of the Atom • Results of the Rutherford experiment (a) The results that the metal foil experiment would have yielded if the plum pudding model had been correct (b) Actual results
B. Introduction to the Modern Concept of Atomic Structure • Ernest Rutherford showed that atoms have internal structure. • The nucleus, which is at the center of the atom, contains protons (positively charged) and neutrons (uncharged). • Electrons move around the nucleus. The Discovery of the Atomic Nucleus
B. Introduction to the Modern Concept of Atomic Structure Comparing the Parts of an Atom
Large Hadron Collider video Circular tunnel 27km in circumference near Geneva Protons or lead nucleii smashed into targets $4 billion cost – limited operation to date
C. Isotopes • Isotopes are atoms with the same number of protons but different numbers of neutrons.
C. Isotopes • A particular isotope is represented by the symbol . e.g. Carbon: What is Z for 12C, 13C and 14C?
Isotopes • True or False? Atoms that have the same number of neutrons but different number of protons are called isotopes • True or False? The mass number of a nucleus represents the number of protons in the nucleus • Are all atoms of the same element identical? If not, how do they differ? Is this consistent with Dalton’s atomic theory?
Isotope Math • What is the symbol for the isotopes below? • Z = 8, number of neutrons = 9 • Isotope of chlorine with A = 37 • Z = 27, A = 60 • Number of protons = 26, number of neutrons = 31 • The isotope of iodine with a mass number of 131 • Z = 3, number of neutrons = 4 • WOC page 88 - Q 29, 30