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Unit 2: The Atom and Periodic Table ISOTOPES REVIEW Atomic symbol Atomic number Protons 2 Neutrons Electrons Atomic mass 6 11 31 24 37 28 REVIEW… FIX THE ERROR Protons have a positive charge and are located on the outer portion of the atom. REVIEW … FIX THE ERROR The gold foil experiment showed that the nucleus has a dense negative center, called the nucleus. REVIEW … FIX THE ERROR Neutrons have the same mass as protons and are located inside of the nucleus. REVIEW … FIX THE ERROR Electrons have a mass of 1.00 amu and are located on the outer portion of the atom. ISOTOPE DEFINITION Atoms of same element with different numbers of neutrons. ISOTOPIC NOTATION A way to represent an isotope Mass of Isotope Atomic Number Element Symbol Give Isotopic Notation for Carbon-13 EXAMPLES Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms. 12C 6 13C 6 14C 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______ PRACTICE An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 B. 2) 35 3) 65 Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67 PRACTICE Write the atomic symbols for atoms with the following: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________ ATOMIC MASSES OR MASS NUMBER A scale designed for atoms gives their small atomic masses in atomic mass units (amu) Listed on the periodic table Average atom based on all the isotopes and their abundance % Atomic mass is not a whole number Na 22.99 ATOMIC MASSES OR MASS NUMBER Each atomic weight is multiplied by its percent abundance (expressed as a decimal). Add the results together Round off to an appropriate number of significant figures. CALCULATING AVERAGE ATOMIC MASS Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% 25Mg = 25.0 amu 10.13% 26Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = PRACTICE Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass)