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LESSON-5-ISOTOPES.pdf
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- 2. Isotopes ◦Atoms of thesame element with different mass numbers. Mass # Atomic # • Nuclear symbol: • Hyphen notation: carbon-12 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem 12 6 C
- 3. Isotopes + + + + + + Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons6 Electrons 6 Nucleus Electrons Carbon-14 Neutrons 8 Protons 6 Electrons 6 + + + + + + Nucleus Neutron Proton
- 4. 3 p+ 3 n0 2e–1e– 3 p+ 4 n0 2e– 1e– 6Li 7Li + + + Nucleus Electrons Nucleus Neutron Proton Lithium-6 Neutrons 3 Protons 3 Electrons 3 Nucleus Electrons Nucleus Neutron Proton Lithium-7 Neutrons 4 Protons 3 Electrons 3 + + +
- 5. Isotopes ◦ Chlorine-37 ◦ atomic#: ◦ mass #: ◦ # of protons: ◦ # of electrons: ◦ # of neutrons: 17 37 17 17 20 Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Cl 37 17 37 17 Cl
- 6. atomic mass: theweighted average of the masses of the isotopes of an element. atomic mass unit (amu): a unit of mass equal to one-twelfth the mass of a carbon-12 atom
- 7. Relative Atomic Mass ◦12Catom = 1.992 × 10-23 g • 1 p = 1.007276 amu 1 n = 1.008665 amu 1 e- = 0.0005486 amu • atomic mass unit (amu) • 1 amu = 1/12 the mass of a 12C atom + + + + + + Nucleus Electrons Nucleus Neutron Proton Carbon-12 Neutrons 6 Protons 6 Electrons 6
- 8. Average Atomic Mass ◦weightedaverage of all isotopes ◦on the Periodic Table ◦round to 2 decimal places Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (mass)(%) + (mass)(%) 100
- 10. 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. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (16)(99.76) + (17)(0.04) + (18)(0.20) 100 = 16.00 amu
- 11. Average Atomic Mass ◦EX: Find chlorine’s average atomic mass if approximately 8 of every 10 atoms are chlorine-35 and 2 are chlorine-37. Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem Avg. Atomic Mass = (35)(8) + (37)(2) 10 = 35.40 amu
- 12. ◦ Assume youhave only two atoms of chlorine. ◦ One atom has a mass of 35 amu (Cl-35) ◦ The other atom has a mass of 36 amu (Cl-36) ◦ What is the average mass of these two isotopes? 35.5 amu ◦ Looking at the average atomic mass printed on the periodic table...approximately what percentage is Cl- 35 and Cl-36? 55% Cl-35 and 45% Cl-36 is a good approximation Cl 35.453 17
- 13. Using our estimated% abundance data 55% Cl-35 and 45% Cl-36 calculate an average atomic mass for chlorine. Cl 35.453 17 Average Atomic Mass = (% abundance of isotope "A")(mass "A") + (% "B")(mass "B") AAM = (% abundance of isotope Cl-35)(mass Cl-35) + (% abundance of Cl-36)(mass Cl-36) AAM = (0.55)(35 amu) + (0.45)(36 amu) AAM = (19.25 amu) + (16.2 amu) AAM = 35.45 amu
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- 15. Naming Isotopes Put themass number after the name of the element ◦carbon- 12 ◦carbon -14 ◦uranium-235 California WEB
- 20. Using a periodictable and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: Element Symbol Atomic Number Atomic Mass # of protons # of neutron # of electron charge 8 8 8 Potassium 39 +1 Br 45 -1 30 35 30 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
- 21. Using a periodictable and what you know about atomic number, mass, isotopes, and electrons, fill in the chart: Element Symbol Atomic Number Atomic Mass # of protons # of neutron # of electron charge 8 8 8 Potassium 39 +1 Br 45 -1 30 35 30 Oxygen Bromine Zinc O K Zn 8 19 35 16 80 19 35 30 20 65 18 36 0 0 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 A N S W E R K E Y