Copyright© by Houghton Mifflin Company. All rights reserved. Atomic Structure

2 Composition of the Atom

3 An atom viewed in cross section.

4 It takes 190,000,000 copper atoms to span the diameter of a penny!!!!!

5 Is it possible that there is no God? Consider the following logic: The universe had a beginning All things that begin need a beginner Therefore, the universe had a beginner It is inescapable that something It is inescapable that something created the universe! created the universe! We call that something “God” We call that something “God” Given what we know about the universe, God is immensely powerful! Given what we know about the universe, God is immensely powerful!

6 Atom Smallest particle of an element that retains the chemical identity of the element Smallest particle of an element that retains the chemical identity of the element Remember: elements are pure substances Remember: elements are pure substances

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8 Atomic Microscopy Scanning Electron Microscope--SEM Gold Atomic Structure 5nm Silicon Atoms Atomic Diameter = 0.234nm

9 Dalton’s Atomic Theory of Matter Each element composed of tiny particles called atoms Each element composed of tiny particles called atoms All atoms of a given element are identical—but different from all others All atoms of a given element are identical—but different from all others Atoms cannot be subdivided, created, or destroyed in chemical reactions Atoms cannot be subdivided, created, or destroyed in chemical reactions Atoms of different elements combine in simple whole number ratios to form compounds Atoms of different elements combine in simple whole number ratios to form compounds In chemical reactions, atoms are combined, separated, or rearranged. In chemical reactions, atoms are combined, separated, or rearranged.

10 Greeks Through the 1700’s Democritus 450 BC All matter composed of “atomos” All matter composed of “atomos” Aristotle disagreed: Aristotle disagreed: What holds these atomos together? What holds these atomos together?Lavoisier Law of Conservation of Matter Law of Conservation of MatterProust Law of constant composition Law of constant composition Compounds have same proportions by mass Compounds have same proportions by mass

11 Discovering Atomic Structure Franklin— Franklin— Kite in a thunderstorm story Kite in a thunderstorm story Concluded that objects have two kinds of charge: + - (like repel) Concluded that objects have two kinds of charge: + - (like repel) Lightning is static electricity on a large scale Lightning is static electricity on a large scale Where do charges come from? Where do charges come from? Faraday—1839 Faraday—1839 Atomic structure related to electricity Atomic structure related to electricity Electricity comes from Greek “elektron” Electricity comes from Greek “elektron” After many experiments—Atoms contain particles that have electric charge After many experiments—Atoms contain particles that have electric charge

12 Sub Atomic Particles Much of Dalton’s theory is still accepted today Much of Dalton’s theory is still accepted today Exception: Exception: Atoms are divisible into subatomic particles Atoms are divisible into subatomic particles Protons Protons Neutrons Neutrons Electrons Electrons In 1897 English physicist J. J. Thompson discovered the electron In 1897 English physicist J. J. Thompson discovered the electron Electrons are negatively charged particles. Electrons are negatively charged particles.

13 Cathode Ray Tube Thompson used the CRT to investigate electrons

14 Thompson modified the CRT as shown below A paddle wheel was placed in the stream of electrons. The electron beam made the wheel spin leading to the conclusion that electrons have mass.

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16 J. J. Thompson ( ) In Thompson modified the CRT Thompson modified the CRT Concluded: cathode ray composed of negatively charged particles Concluded: cathode ray composed of negatively charged particles 1.76 x 10 8 Coulombs/gram 1.76 x 10 8 Coulombs/gram Thompson concluded that negative particles issued from the cathode Thompson concluded that negative particles issued from the cathode Meant that atoms have a substructure Meant that atoms have a substructure If there were negative parts of the atom, then there must be positive parts of the atom because atoms are normally neutral If there were negative parts of the atom, then there must be positive parts of the atom because atoms are normally neutral

17 Mass of an Electron Thompson was not able to determine charge of single electron Thompson was not able to determine charge of single electron Millikan’s oil drop experiment did that Millikan’s oil drop experiment did that Milikan determined Milikan determined Charge of electron = 1.60 x coulombs Charge of electron = 1.60 x coulombs Mass of electron = 9.11 x grams Mass of electron = 9.11 x grams Mass of electron = x kg Mass of electron = x kg 1/2000 th the mass of a hydrogen atom 1/2000 th the mass of a hydrogen atom

18 Thompson Plum Pudding model of an atom.

19 Properties of Subatomic Particles

20 Rutherford’s experiment circa 1909 (alpha scattering experiment) 1/8000 alpha particle were deflected Like a Toyota hitting a Mack truck!! Rutherford had discovered the nucleus

21 Alpha particles scattered from the gold foil

22 Result of Rutherford Gold Foil Experiment

23 Results of foil experiment if Plum Pudding model had been correct.

24 Atomic Number 4.3

25 Modern Atomic Theory Atoms composed of protons, neutrons and electrons. Atoms composed of protons, neutrons and electrons. Protons and neutrons form the nucleus Protons and neutrons form the nucleus Electrons move in the space outside the nucleus Electrons move in the space outside the nucleus Atomic number = number of protons Atomic number = number of protons Ions are atoms with a charge Ions are atoms with a charge Ionic charge = #protons - #electrons Ionic charge = #protons - #electrons Isotopes are atoms with the same number of protons but different number of neutrons Isotopes are atoms with the same number of protons but different number of neutrons Hydrogen-1protium Hydrogen-1protium Hydrogen-2 deuterium Hydrogen-2 deuterium Hydrogen-3Tritium Hydrogen-3Tritium

26 Figure 3.10: Two isotopes of sodium. Mass # Symbol Atomic # Mass # = Atomic # + # neutrons

27Isotopes

28 Chemical Symbols Al Se Al Se 1334 #protons = ? #neutrons = ? # electrons = ?

29 Atomic Mass

30 Atomic Mass The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element. The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element. A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature. A weighted average mass reflects both the mass and the relative abundance of the isotopes as they occur in nature.

31 Atomic Mass

32 AMU 1/12 mass of a carbon atom = 1.66 x g =1amu 1/12 mass of a carbon atom = 1.66 x g =1amu Chlorine AMU Chlorine AMU Atomic mass on periodic table is really average atomic mass in AMU’s Atomic mass on periodic table is really average atomic mass in AMU’s For Chlorine Atomic Mass =.7577 x x = Chlorine 35 Chlorine 37 Chlorine 35 Chlorine 37

33 Periodic Table A periodic table is an arrangement of elements in Which the elements are separated into groups based on a set of repeating properties.

34 Nuclear Stability Nucleus held together by strong nuclear forces Nucleus held together by strong nuclear forces Occur for objects very close together Occur for objects very close together Neutrons are glue Neutrons are glue Provide SNF without repulsion Provide SNF without repulsion ++nn + nn +

35 Belt of Stability # protons (atomic #) #neutrons More than one neutrons for every proton One proton for every neutron Atomic # = 20

36 Radioactive Particles

37 Radioactive Particles Ernest Rutherford ( ) In early 1900’s experimented with radioactive materials In early 1900’s experimented with radioactive materials ChargeName Penetrating Ability  -particle2+alpha stopped by paper  -particle1-beta stopped by foil/clothes  -raynonegamma stopped by lead

38 Radioactive Particles Composition  -particlehelium nuclei (2 protons & 2 Neutrons)  -particleelectron  -ray high energy radiation

39 Radioactive Decay Alpha Decay

40 Fusion

41 The Positively Charged Nucleus Henry Mosely ( ) Henry Mosely ( ) Every element contains a unique positive charge in its nucleus Every element contains a unique positive charge in its nucleus

42 The Periodic Table.

43 The ions formed by selected members of groups 1, 2, 3, 6, and 7. Ionic Charge = Atomic Number - # electrons

44 Top Ten

45 Top Ten

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51 Antares is the 15th brightest star in the sky. It is more than 1000 light years away!