Chapter 4 Atomic Structure 4.1 Defining the Atom 4.2 Structure of the Nuclear Atom 4.3 Distinguishing Among Atoms Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Early Models of the Atom Atom: smallest particle of an element that retains its identity in a chemical reaction. Atomos – Greek word for indivisible Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atoms contain 3 types of subatomic particle Key Concepts Atoms contain 3 types of subatomic particle Subatomic Particle Symbol Charge Location Proton p+ +1 nucleus Neutron n0 Electron e- -1 surrounding nucleus Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

It’s like an ID number for an element Atomic Number Atomic Number: number of protons in the nucleus of an atom of that element It’s like an ID number for an element

Mass Number Mass Number: total number of protons and neutrons in an atom Hyphenated notation: Helium-4

Mass of Subatomic Particles Relative mass (mass of proton = 1) Interpret Data Mass of Subatomic Particles Particle Relative mass (mass of proton = 1) Actual mass (g) Proton 1 amu 1.67  10–24 Neutron Electron 1/1840 amu 9.11  10–28 Atomic Mass Unit: 1/12 of the mass of a Carbon-12 atom Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atoms If you know the atomic number and mass number, you can determine the atom’s composition. # Protons = Atomic Number # Electrons = # Protons (for a neutral atom) # Neutrons = Mass Number – Atomic Number

Determining the Composition of an Atom Sample Problem 4.2 Determining the Composition of an Atom How many protons, electrons, and neutrons are in each atom? Protons: 4 10 11 Neutrons: 5 10 12 Electrons: 4 10 11 a. Be b. Ne c. Na 9 4 20 10 23 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Isotopes Isotopes: atoms that have the same number of protons but different numbers of neutrons. Neon-20, neon-21, and neon-22 are three isotopes of neon. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Isotopes Do Now: Determine the number of protons, neutrons, and electrons for the following neutral atoms: http://www.pbs.org/wgbh/nova/education/physics/radioactive-decay-carbon.html Protons Electrons Neutrons Nuclear Symbol Magnesium-24 Magnesium-25 Magnesium-26 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Most elements occur as a mixture of two or more isotopes. http://www.pbs.org/wgbh/nova/education/physics/radioactive-decay-carbon.html Mass (amu) Relative Abundance Magnesium-24 23.985 78.99% Magnesium-25 24.986 10.00% Magnesium-26 25.983 11.01% Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Interpret Data Natural Percent Abundance of Stable Isotopes of Some Elements Name Symbol Natural percent abundance Mass (amu) Atomic mass Hydrogen H 99.985 0.015 negligible 1.0078 2.0141 3.0160 1.0079 Helium He 0.0001 99.9999 4.0026 Carbon C 98.89 1.11 12.000 13.003 12.011 Oxygen O 99.759 0.037 0.204 15.995 16.995 17.999 15.999 Chlorine Cl 75.77 24.23 34.969 36.966 35.453 35 17 37 1 2 3 12 6 13 4 18 8 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Mass Atomic mass - weighted average mass of atoms in a naturally occurring sample of the element. reflects both mass and relative abundance of the isotopes Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

If a student’s grade is weighted per the table below, what would their grade be? Average Tests 50% 79 Classwork 30% 95 Homework 20% 85

Calculating Average Atomic Mass Chlorine-35 has an amu of 34.9689 with an abundance of 75.771% while Chlorine-37 has an amu of 36.9659 and an abundance of 24.229%. What is the average atomic mass of chlorine? 35.453 Carbon-12 (12.00 amu) makes up 98.93% of all of the carbon atoms, while carbon-13 (13.003 amu) is about 1.07% abundant. What is the average atomic mass of carbon? 12.011

Radioactivity: release of energy & matter that results from changes in the nucleus of an atom All elements with an atomic number greater than 83 are radioisotopes (unstable nucleii) Elements with atomic numbers less than or equal to 83 have isotopes with stable nucleii and may have a radioactive isotope http://www.pbs.org/wgbh/nova/education/physics/radioactive-decay-carbon.html

END OF CHAPTER 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.