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Explore atoms as the fundamental units of matter and learn about isotopes, atomic mass calculations, and the classification of elements on the periodic table. Understand the structure of atoms, including protons, neutrons, and electrons, as well as the significance of atomic number and mass. Discover the distinguishing features between isotopes and delve into the properties of metals, nonmetals, metalloids, and noble gases in the periodic table.
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Chapter 5 Atomic Structure & The Periodic Table
Atoms • The smallest particle of an element that retains the properties of that element.
Dalton’s Atomic Theory (1808) • Each element is made up of tiny particles called atoms. • The atoms of a given element are identical. • Chemical compounds are formed when atoms combine with each other. • Chemical reactions involve reorganization of the atoms
J. J. Thomson • Cathode Ray Tube • Discovered the electrons • Cathode rays bent towards the positive plate
A schematic representation of the apparatus Millikan used to determine the charge on the electron.
(a) The expected results of the metal foil experiment if Thomson's model were correct. (b)Actual results.
Building Blocks of Atoms Subatomic particles • Protons, electrons, and neutrons Nucleus • Protons & neutrons Where are the electrons? • They surround the nucleus.
Periodic Table • Atomic Number = # of protons • Element Symbols (1-2 letters) • Groups / Families = columns • Similar properties • Periods = rows
Distinguishing Between Atoms • Atomic # = # protons = # electrons • Isotopes: # of protons remains the same, but # of neutrons vary • Example: 3 isotopes of hydrogen • Protium (0 neutrons) • Deuterium (1 neutron) • Tritium (2 neutrons) • Mass # = protons + neutrons
Mass # A Element Symbol ZX Atomic #
Atomic Mass • Elements occur in nature as mixtures of isotopes • Carbon = 98.89% 12C 1.11% 13C <0.01% 14C • Carbon atomic mass = 12.01 amu
Copper has two naturally occurring isotopes: copper-63 and copper-65 69.17% of copper-63; the mass is 62.94 amu 30.83% of copper-65; the mass is 64.93 amu Calculate the average atomic mass.
Average atomic mass of copper = (.6917 x 62.94 amu) + (.3083 x 64.93 amu) = 63.55 amu
Periodic Table (cont.) • METALS: cover the largest region of the periodic table • Good conductors of heat and electricity, ductile, and malleable • NONMETALS: most of them are gases • Poor conductors of heat and electricity • METALLOIDS: elements that have some properties of metals and nonmetals • NOBLE GASES: extremely unreactive or inert
Classification of elements as metals, nonmetals, and metalloids.