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1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Atom Proton Nucleus Neutron Electron Mass number Atomic number Atomic mass unit Isotope Atomic Mass • First column: words • Second column: definition from text • Third column: definition in your own words • Fourth column: Picture or example Due Tomorrow! SC3. Students will use the modern atomic theory to explain characteristics of atoms. “Atomic Theory and Structure” OBJECTIVES: Explain Dalton’s atomic theory. Identify the parts of an atom, their location, charge, and relative mass. Determine the numbers of subatomic particles in an atom. Democritus’s Atomic Philosophy Democritus- all matter is made up of imperishable, indivisible units, which he called atoma. Dalton’s Atomic Theory 1)All elements are composed of atoms. John Dalton (1766 – 1844) 2) Atoms of the same element are identical. Atoms of different elements are different. 3) Atoms of different elements can combine to form compounds. 4) In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element. Modern Theory One change to Dalton’s atomic theory is that atoms are divisible into subatomic particles: Electrons Protons Neutrons The Subatomic Particles Location Charge Relative mass in amu Proton Neutrons Electrons 0.00055 amu amu: mass of 1/12 of a carbon atom Function Atom Math Atomic number: number of protons (and electrons IF atom is neutral) Atomic mass: called mass number when rounded to nearest whole number. Mass Number equals protons + neutrons. Atom Math Protons: atomic number Electrons: same as protons if atom is neutral Neutrons: mass number – atomic number protons: ________ neutrons: ________ electrons: ________ Element carbon Phosphorus Gold Atomic Number Number of Protons Number of Electrons Number of Neutrons Symbol Shorthand Carbon Superscript → Subscript → Mass number Atomic number X Phosphorus Gold Work Session Subatomic Particle Counting WS—15 minutes Atomic Structure Part 2“Isotopes and Ions” Ions When an atom loses or gains electrons it is called an ion. The number of electrons lost or gained is indicated by a charge. Element Protons Oxygen Gains 2 electrons Aluminum Loses 3 electrons Beryllium Loses 2 electrons Bromine Gains 1 electron Electrons Ion Assignment Ion Practice Set Finish for homework Ion Review Element Sulfur Sodium Boron Number of protons Number of Electrons Gains 2 electrons Loses 1 electron loses 3 electrons Ion Atomic Structure Part 2“Isotopes and Ions” Isotopes Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers. Naming Isotopes To distinguish between isotopes of the same element, put the mass number after the name of the element: A Z Oxygen-18 Aluminum-25 10Be (beryllium-10) 79 Br (bromine-79) Potassium-41 X Protons Neutrons Isotopes Elements occur in nature as mixtures of isotopes. So, atoms of the same element aren’t necessarily the same…. Isotope Review Protons Carbon-12 Carbon-14 Uranium-238 Uranium-235 Hydrogen-1 Hydrogen-2 Hydrogen-3 Neutrons Work Session Complete Ion Practice Set and Isotope Practice Sets (15 minutes) Atomic Mass The average atomic mass: is based on the abundance (percentage) of each variety of that element in nature. Lesson Preview Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon’s reported atomic mass, which isotope do you think is the most abundant in nature? Poll everywhere response To calculate the average atomic mass: Multiply the atomic mass of each isotope by it’s abundance percentage (expressed as a decimal), then add the results. Atomic Masses Atomic mass is the average of all the naturally occurring isotopes of that element. Isotope Carbon-12 Atomic % in mass nature 98.89% Carbon-13 1.11% Carbon-14 <0.01% negligible Carbon = 12.011 Average Atomic Mass Rubidium has two common isotopes, Rb-85 and Rb-87. If the abundance of Rb-85 is 72.2% and the abundance of Rb-87 is 27.8%, what is the average atomic mass of rubidium? On Your Own Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%), 49Ti (5.5%), 50Ti (5.3%). What is the average atomic mass of titanium? Beanium Lab Purpose: To illustrate the relationship between isotopic mass, isotopic abundance, and atomic mass. Lab Hints Read the instructions! Everyone participate in counting beans. Do not lose your beans and clean up when you are finished. Work on the following assignments: ◦ Beanium Lab ◦ Average Atomic Mass Practice Worksheet