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Atomic Structure Chapter 4 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Elements are composed of extremely small particles called atoms. Structure of Atoms Structure of the Atom Subatomic Particles Mass (g) Particle - Charge (Coulombs) -28 -19 -1 1.67 x 10-24 +1.6 x 10-19 +1 Electron (e ) 9.1 x 10 Proton (p+) Charge (units) Neutron (n) 1.67 x 10-24 -1.6 x 10 0 0 mass p = mass n = 1840 x mass e- 2.2 Particle Charge Mass (atomic mass units) 1 Location Proton positive + Neutron neutral Ø 1 nucleus Electron negative - 0.0006 orbit, level, cloud nucleus • Nucleus – Center of the atom – Protons and neutrons – 99.9% of the atom’s mass is here – About 100,000 times smaller than the entire atom Atomic Number = number of protons in atom - identifies the element - only constant number Atomic Mass = mass of protons AND neutrons Counting p, e, n Atomic number = number of protons in nucleus Atomic Mass number = number of protons + number of neutrons Number of Neutrons = rounded atomic mass – atomic number Number of electrons = Number of protons (in a neutral atom) Element Hydrogen (H) Oxygen (O) Copper (Cu) Barium (Ba) Iodine (I) # of protons # of electrons # of neutrons Isotopes Alternative forms of an element that differ in their number of neutrons How are these atoms different from each other? 2.3 Writing Symbols for Isotopes Mass Number X Atomic Number 1 1H 235 92 Element Symbol 2 1H U 3 1H 238 92 U Do You Understand Isotopes? How many protons, neutrons, and electrons are in-- 14 6 C 11 6 C? ? 6 protons, 8 (14 - 6) neutrons, 6 electrons How many protons, neutrons, and electrons are in-6 protons, 5 (11 - 6) neutrons, 6 electrons