Symbols Contain the symbol of the element, the mass number and the atomic number X Mass number Atomic # protons + # neutrons mass number # protons

F Symbols 19 9 Find the number of protons number of neutrons number of electrons Atomic number Mass number = 9 + F 19 9 = 10 = 9 = 9 http://ptcl.chem.ox.ac.uk/MSDS/glossary/corrosive.jpg = 19

Br Symbols 80 35 Find the number of protons number of neutrons number of electrons Atomic number Mass number = 35 = 45 Br 80 35 = 35 = 35 = 80 http://www.chem.purdue.edu/gchelp/liquids/bromine.gif

Na Symbols 23 11 Find the number of protons number of neutrons number of electrons Atomic number Mass number = 11 = 12 Na 23 = 11 = 11 11 http://www.webelements.com/webelements/elements/media/element-pics/Na.jpg = 23 Sodium atom

Na Symbols 23 11 Find the 1+ number of protons number of neutrons number of electrons Atomic number Mass number = 11 Na = 12 23 1+ = 10 11 = 11 = 23 Sodium ion

Symbols If an element has an atomic number of 23 and a mass number of 51 what is the number of protons number of neutrons number of electrons Complete symbol = 23 = 28 = 23 http://www.klenktools.com/Main/Images/All-combo-wrenches-sm.jpg V 51 23

Symbols If an element has 60 protons and 84 neutrons what is the Atomic number Mass number number of electrons Complete symbol = 60 = 144 = 60 http://www.stevespanglerscience.com/img/cache/02268c260f8fff6f7502dd93a20e39be/WMLN-100-260x250.jpg Nd 144 60

Symbols If a neutral atom of an element has 78 electrons and 117 neutrons what is the Atomic number Mass number number of protons Complete symbol = 78 = 195 = 78 Platinum is even more rare than gold. In fact, 50 tons of ore is required to produce just 50 grams of platinum. Platinum is a grayish-white metal that is malleable yet, like gold, is resistant to attack by air, moisture, and most solutions. Its melting point is even higher than gold, at just over 3,000°F. It ranks 72 in abundance among the elements. http://www.patbakersfinejewelry.com/graphics/platinum%20bar.jpg Pt 195 78

C Isotopes Mass # Atomic # 12 6 Atoms of the same element with different mass numbers. Nuclear symbol: 12 6 C Mass # Each isotope has a different number of neutrons. Atomic # Hyphen notation: carbon-12 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Isotopes Neutron + Electrons Nucleus Nucleus Proton Proton Nucleus Carbon-12 Neutrons 6 Protons 6 Electrons 6 Electrons The chemistry of each element is determined by its number of protons and electrons. In a neutral atom, the number of electrons equals the number of protons. Symbols for elements are derived directly from the element’s name. Nuclei of atoms contain neutrons as well as protons. The number of neutrons is not fixed for most elements, unlike protons. Atoms that have the same number of protons, and hence the same atomic number, but different numbers of neutrons are called isotopes. Carbon-14 Neutrons 8 Protons 6 Electrons 6 Nucleus

6Li 7Li 3 p+ 3 n0 3 p+ 4 n0 2e– 1e– 2e– 1e– Nucleus Neutron Proton Electrons + Electrons + Nucleus Nucleus Lithium-6 Lithium-7 Neutrons 3 Protons 3 Electrons 3 Neutrons 4 Protons 3 Electrons 3

Cl Isotopes 37 17 Cl Chlorine-37 atomic #: mass #: # of protons: # of electrons: # of neutrons: 17 37 20 37 17 Cl Atoms that have the same number of protons, and hence the same atomic number, but different numbers of neutrons are called isotopes. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Relative Atomic Mass 12C atom = 1.992 × 10-23 g atomic mass unit (amu) 1 amu = 1/12 the mass of a 12C atom Neutron + 1 p = 1.007276 amu 1 n = 1.008665 amu 1 e- = 0.0005486 amu Electrons Atomic mass 1. The mass of any given atom is not simply the sum of the masses of its electrons, protons, and neutrons. 2. Atoms are too small to measure individually and do not have a charge. 3. The arbitrary standard that has been established for describing atomic mass is the atomic mass unit (amu), defined as one-twelfth of the mass of one atom of 12C. 4. Most elements exist as mixtures of several stable isotopes. The weighted average is of the masses of the isotopes is called the atomic mass. 5. Electrons added or removed from an atom produce a charged particle called an ion, whose charge is indicated by a superscript after the symbol for the element. Nucleus Proton Nucleus Carbon-12 Neutrons 6 Protons 6 Electrons 6

Average Atomic Mass Avg. (mass)(%) + (mass)(%) Atomic Mass 100 weighted average of all isotopes on the Periodic Table round to 2 decimal places Avg. Atomic Mass (mass)(%) + (mass)(%) = 100 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Average Atomic Mass EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16O, 0.04% 17O, and 0.20% 18O. Avg. Atomic Mass (16)(99.76) + (17)(0.04) + (18)(0.20) 16.00 amu = = 100 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Average Atomic Mass (35)(8) + (37)(2) 10 Avg. Atomic = = Mass EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. Avg. Atomic Mass (35)(8) + (37)(2) = = 35.40 amu 10 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Cl 35.4594 17 100 Mass spectrum of chlorine. Elemental chlorine (Cl2) contains only two isotopes: 34.97 amu (75.53%) and 36.97 (24.47%) 90 80 Cl-35 70 AAM = (34.97 amu)(0.7553) + (36.97 amu)(0.2447) 60 AAM = (26.412841 amu) + (9.046559 amu) AAM = 35.4594 amu 50 Abundance 40 30 Cl-37 Mass spectrum of chlorine. Elemental chlorine (Cl2) contains only two isotopes: 34.97 amu (75.53%) and 36.97 (24.47%) 20 10 34 35 36 37 Mass

Mass Spectrophotometer magnetic field heaviest ions stream of ions of different masses lightest ions electron beam gas Dorin, Demmin, Gabel, Chemistry The Study of Matter 3rd Edition, page 138

Weighing atoms ions accelerate towards charged magnetic field gas sample enters here filament current ionizes the gas ions accelerate towards charged slit magnetic field deflects lightest ions most ions separated by mass expose film .                                                                                                                                                                                                                           The first mass spectrograph was built in 1919 by F. W. Aston, who received the 1922 Nobel Prize for this accomplishment mass spectrometry is used to experimentally determine isotopic masses and abundances interpreting mass spectra       average atomic weights - computed from isotopic masses and abundances - significant figures of tabulated atomic weights gives some idea of natural variation in isotopic abundances Copyright © 1997-2005 by Fred Senese

Mass Spectrometry 198 200 202 Photographic plate 196 199 201 204 - + 196 199 201 204 198 200 202 Mass spectrum of mercury vapor Photographic plate A gaseous sample is ionized by bombarding it with electrons in the lower part of the apparatus (not shown), producing positive ions. The ions pass through an electric field in which they are brought to a particular velocity. The ions then pass through a narrow slit into a curved chamber. A magnetic field is applied perpendicular to the beam of ions. All the ions with the same mass-to-charge ratio are deflected into the same circular path. (In most cases, the ionic charge is 1+ and the mass-to-charge ratio is the same as the mass.) Modern spectrophotometers use electronic detection devices (TOF = time of flight detectors) rather than photographic plates or film to establish mass-to-charge ratios and relative number of ions. - + Stream of positive ions Hill, Petrucci, General Chemistry An Integrated Approach 1999, page 320

Mass Spectrum for Mercury (The photographic record has been converted to a scale of relative number of atoms) The percent natural abundances for mercury isotopes are: Hg-196 0.146% Hg-198 10.02% Hg-199 16.84% Hg-200 23.13% Hg-201 13.22% Hg-202 29.80% Hg-204 6.85% 198 200 202 30 25 20 15 10 5 196 199 201 204 Mass spectrum of mercury vapor Relative number of atoms 196 197 198 199 200 201 202 203 204 Mass number

The percent natural abundances for mercury isotopes are: Hg-196 0.146% Hg-198 10.02% Hg-199 16.84% Hg-200 23.13% Hg-201 13.22% Hg-202 29.80% Hg-204 6.85% A B C D E F G Hg 200.59 80 (% "A")(mass "A") + (% "B")(mass "B") + (% "C")(mass "C") + (% "D")(mass "D") + (% "E")(mass "E") + (% F)(mass F) + (% G)(mass G) = AAM (0.00146)(196) + (0.1002)(198) + (0.1684)(199) + (0.2313)(200) + (0.1322)(201) + (0.2980)(202) + (0.0685)(204) = x 0.28616 + 19.8396 + 33.5116 + 46.2600 + 26.5722 + 60.1960 + 13.974 = x x = 200.63956 amu

Isotopes, cont. Objectives: To draw a diagram of an atom given its atomic notation. To explain and illustrate the concept of isotopes. To explain the concept of relative atomic mass. To calculate the atomic mass for an element given the mass and abundance of the naturally occurring isotopes.

Isotopes Dalton was wrong. Atoms of the same element can have different numbers of neutrons different mass numbers called isotopes The word isotope comes from the Greek words isos, meaning "equal," and topos, meaning "place." C-12 vs. C-14 California WEB

Naming Isotopes Put the mass number after the name of the element carbon- 12 carbon -14 uranium-235 California WEB

Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: Element Symbol Atomic Number Mass # of protons # of neutron # of electron charge 8 Potassium 39 +1 Br 45 -1 30 35 Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > Electrons Ion (anion) : Electrons > Protons

Using a periodic table and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: A N S W E R K E Y Element Symbol Atomic Number Mass # of protons # of neutron # of electron charge 8 Potassium 39 +1 Br 45 -1 30 65 Oxygen O 8 16 K 19 19 20 18 Bromine 35 80 35 36 Zinc Zn 30 35 Atomic Number = Number of Protons Number of Protons + Number of Neutrons = Atomic Mass Atom (no charge) : Protons = Electrons Ion (cation) : Protons > Electrons Ion (anion) : Electrons > Protons

Isotopes Because of the existence of isotopes, the mass of a collection of atoms has an average value. Average mass = ATOMIC WEIGHT Boron is 20% B-10 and 80% B-11. That is, B-11 is 80 percent abundant on earth. For boron atomic weight 0.20 (10 amu) + 0.80 (11 amu) = 10.8 amu

Atomic Mass Magnesium has three isotopes. 78.99% magnesium 24 with a mass of 23.9850 amu, 10.00% magnesium 25 with a mass of 24.9858 amu, and the rest magnesium 26 with a mass of 25.9826 amu. What is the atomic mass of magnesium? If not told otherwise, the mass of the isotope is the mass number in amu. Isotope Percent Abundance Mass Mg-24 78.99 23.9850 Mg-25 10.00 24.9585 Mg-26 25.9826 18.94575 2.49585 Atomic mass is not a whole number because it is an average. This is why their are the decimal numbers on the periodic table. http://www.trustedreviews.com/images/article/inline/4066-Flashbulb.jpg 11.01 2.86068 24.304 amu California WEB

Atomic Mass Calculate the atomic mass of copper if copper has two isotopes. 69.1% has a mass of 62.93 amu and the rest has a mass of 64.93 amu. Isotope Percent Abundance Mass Cu-63 69.1 62.93 Cu-65 64.93 43.48463 30.9 20.06337 63.548 http://upload.wikimedia.org/wikipedia/commons/e/e2/United_States_penny,_obverse,_2002.jpg Cu 29 63.548

Isotopes of Magnesium Atomic symbol Mg Mg Mg 24 12 25 12 26 12 Number of protons 12 12 12 Number of electrons 12 12 12 Mass number 24 25 26 Number of neutrons 12 13 14 Isotope Notation Mg-24 Mg-25 Mg-26 Timberlake, Chemistry 7th Edition, page 64

Isotopes of Hydrogen Protium Deuterium Tritium 1 p+ 1 e- 1 p+ 1 n 1 e- (ordinary hydrogen) (heavy hydrogen) (radioactive hydrogen) H-2 H-3 H-1 Ralph A. Burns, Fundamentals of Chemistry 1999, page 100

Isotopes of Hydrogen Protium (H-1) Deuterium (H-2) Tritium (H-3) 1 proton, 0 neutrons, 1 electron most abundant isotope Deuterium (H-2) 1 proton, 1 neutron, 1 electron used in “heavy water” Tritium (H-3) 1 proton, 2 neutrons, 1 electron radioactive 1 p+ 1 n 1 e- 1 p+ 2 n 1 e-

Isotopes of Three Common Elements Symbol Fractional Abundance Average Atomic Mass Carbon Chlorine Silicon Si 28 29 30 27.977 28.976 29.974 92.21% 4.70% 3.09% Mass Number Mass (amu) 12 6 C 12 12 (exactly) 99.89% 12.01 13 6 C 13.003 1.11% 13 35 17 Cl 35 34.969 75.53% 35.45 37 17 Cl 37 36.966 24.47% 28 14 29 14 28.09 30 14 LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 110

Radioisotopes Radioactive isotopes Many uses Medical diagnostics Optimal composition of fertilizers Abrasion studies in engines and tires Radioisotope is injected into the bloodstream to observe circulation.

Half-Life of Isotopes Half-Lives and Radiation of Some Naturally Occurring Radioisotopes Isotope Half-Life Radiation emitted Carbon-14 5.73 x 103 years b Potassium-40 1.25 x 109 years b, g Radon-222 3.8 days a Radium-226 1.6 x 103 years a, g Thorium-230 7.54 x 104 years a, g Thorium-234 24.1 days b, g Uranium-235 7.0 x 108 years a, g Uranium-238 4.46 x 109 years a

Atomic Structure ATOMS IONS ISOTOPES Differ by number of protons Differ by number of electrons ISOTOPES Differ by number of neutrons

Island of Stability, (13:10) https://www.youtube.com/watch?v=pkV63_Y6Klw