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Atom’s Story. How We Know What We Can’t See Looks Like Day 4 Average Atomic Mass. Isotopes. Atoms of the same element (they have the same number of protons) that have different masses because they have different numbers of neutrons. C. C. 13. C. 14. C. 11. 12. - PowerPoint PPT Presentation
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How We Know What We Can’t See Looks Like
Day 4 Average Atomic Mass
IsotopesAtoms of the same element (they have the same
number of protons) that have different masses because they have different numbers of neutrons.
C C C C11 12 13 14
C12
6
Carbon – 12 makes up the greatest % of carbon in the universe
MASS #
ATOMIC #
Relative masses on the P. Table are weighted averages of the isotopes.
Atomic Masses
Isotope Symbol Composition of the nucleus
% in nature
Carbon-12
12C 6 protons6 neutrons
98.88%
Carbon-13
13C 6 protons7 neutrons
1.11%
Carbon-14
14C 6 protons8 neutrons
<0.01%
Atomic mass is the average of all the naturally isotopes of that element.
Carbon = 12.011
Average Atomic Mass = Mass Number1 * %1 + Mass Number2 * %2 + …
Average atomic Mass Carbon = 12 * .9888 + 13 * 0.0111 + 14 * 0.0001
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