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Name_____________________________________ Chemistry Atomic Structure Essential Question: How was the structure of the atom determined? Vocabulary: Atom Atomic mass Atomic mass unit Atomic number Electron Isotope Mass number Neutron Nucleus Proton Lesson 1: Parts of the Atom Key question: What are the parts of the atom? 1. Definition of an atom:________________________________________________________________ 2. Sub-atomic Particle Chart Particle Discovered By/Year Location in Atom Charge Mass in Grams Mass in amu electron proton neutron amu = 1 atomic mass unit or 1/12 the mass of a carbon-12 atom 3. Atomic Number: the number of ____________ in the nucleus of an atom All atoms of the same element have the __________ atomic number Number of naturally occurring elements: _____ Atomic number also tells the number of ____________ in electrically neutral atom. Atomic number discovered by ______________ ______________. On the Periodic Table atomic number is found in the _________ __________ of the element block. Examples: _____ H _____ O _____ N _____ C _____ U _____ Na 4. Isotope: atom of an element with a different number of _________________. Isotopes of Hydrogen: _______________ 1 proton and 0 neutron _______________ 1 proton and 1 neutron _______________ 1 proton and 2 neutrons 5. Mass Number: sum of the _______________ and _______________ On Periodic Table, round atomic mass to nearest whole number to get the mass number. C O Na Fe U Mass Number: _____ _____ _____ _____ _____ Atomic Number: _____ _____ _____ _____ _____ Number of Neutrons: _____ _____ _____ _____ _____ 6. Atomic Mass: _______________ _______________ of all naturally occurring isotopes of an element Standard is the ________________ atom which was established in __________ and has a mass of _________. Problem: If 90.0% of the isotopes of an element have a mass of 35 amu, 8.00% of the isotopes have a mass of 37, and 2.00% have a mass of 38, what is the atomic mass of the element? 12 7. Nuclear Symbols of Elements: C where 12 = ________________ 6 and 1 H 2 H 3 H Ca 6 = ________________ U Na Cl 8. Nucleon- name for any particle in the ______________ of the atom, such as the ____________ and ____________. Practice Worksheet on Atomic Structure 1. Sub-atomic Particles Particle proton neutron electron Mass Charge Location in Atom 2. Definitions _______________ atoms with same atomic numbers but different atomic masses _______________ total number of protons and neutrons in the nucleus _______________ weighted average of the masses of all isotopes of an element _______________ number of protons in the nucleus; also called nuclear charge 3. Fill in the chart of the elements. Element Symbol Atomic Number Mass Number Number Neutrons Nuclear Symbol 4 Helium He 2 Oxygen C 7 23 Na 11 chlorine K 47 gold U iron Study of the Atom 1. Democritus (460 BC-370 BC): a Greek philosopher, believed that atoms were ____________ and_________________. His ideas were based on reasoning, not on experimentation. 2. John Dalton (1766-1844): used Democritus’s ideas and proposed the first atomic theory in 1803 based on experimentation, which included the following ideas: All ____________ consist of tiny indivisible particles called atoms. Atoms of the same element are ____________, different from those of any other element. Atoms of different elements can ____________ mix or chemically ____________ in simple whole number ratios to form compounds. Chemical ____________ occur when atoms are separated, joined, or rearranged. 3. J.J. Thomson (1856-1940): discovered the ____________ in 1897 by using a cathode ray tube. He showed that cathode rays can be deflected by a ____________ and determined the __________ to ____________ ratio of electrons. Cathode rays are really beams of ____________ as in a television. 4. Robert A. Millikan (1868-1953): calculated the __________ and __________ of an electron in 1916. 5. Lord Ernest Rutherford (1871-1937): in 1911 carried out the Gold Foil Experiment which determined : The atom is mostly ____________ ____________. At the center of the atoms is a dense core of ____________ charged particles, called ___________ This central core was called the nucleus. 6. James Chadwick (1891-1974): in 1932 discovered the ____________, which has no charge but a mass nearly equal to that of a ____________.