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WEIGHTED AVERAGE MASS NUMBER:

WEIGHTED AVERAGE MASS NUMBER: 1)The mass number on the periodic table is calculated from the weighted average of the most abundant isotopes . 2) Abundance is presented as a percentage, however it is expressed as a decimal in any calculations.

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WEIGHTED AVERAGE MASS NUMBER:

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  1. WEIGHTED AVERAGE MASS NUMBER: 1)The mass number on the periodic table is calculated from the weighted average of the most abundant isotopes. 2) Abundance is presented as a percentage, however it is expressed as a decimal in any calculations. 3) The most abundant isotope will have a mass number closest to the weighted mass number average. EXAMPLE FOR ELEMENT X, 30%(0.30) OF THE ATOMS ARE X-40, 20%(0.20) ARE X-45 AND 50%(0.50) ARE X-47. NOTE X-40 IS USUSALLY REPRESENTED AS 40X. INTERPRETATION: 30 OUT OF 100 ATOMS ARE X-40 20 OUT OF 100 ATOMS ARE X-45 50 OUT OF 100 ATOMS ARE X-47

  2. SKILL #2)--- WEIGHTED AVERAGE MASS NUMBER CALCULATION. • PERCENTAGE ABUNDANCES TO DECIMALS CONVERT ALL THE. • MULTIPLY THE DECIMAL ABUNDANCE BY THE MASS NUMBER OF THAT ISOTOPE TO GET THE WEIGHTED SUBTOTAL. • ADD THE WEIGHTED SUBTOTALS TO GET THE WEIGHTED AVERAGE MASS NUMBER. • EXAMPLE)--- WEIGHTED AVERAGE MASS NUMBER CALCULATION. • CALCULATE THE MASS NUMBER OF ELEMENT X WHERE,: 30%(0.30) OF THE ATOMS ARE X-40, 20%(0.20) ARE X-45 AND 50%(0.50) ARE X-47 • CONVERT ALL THE PERCENTAGE ABUNDANCES TO DECIMALS. • 20%/100 = 0.20 30%/100=0.30 50%/100=0.50 • .

  3. EXAMPLE)--- WEIGHTED AVERAGE MASS NUMBER CALCULATION. • CALCULATE THE MASS NUMBER OF ELEMENT X WHERE,: 30%(0.30) OF THE ATOMS ARE X-40, 20%(0.20) ARE X-45 AND 50%(0.50) ARE X-47 • CONVERT ALL THE PERCENTAGE ABUNDANCES TO DECIMALS. • 20%/100 = 0.20 30%/100=0.30 50%/100=0.50 • 2)MULTIPLY THE DECIMAL ABUNDANCE BY THE MASS NUMBER OF THAT ISOTOPE TO GET THE WEIGHTED SUBTOTAL

  4. + 44.50 AMU ADD THESE TO GET THE MASS AVERAGE WEIGHTED AVERAGE AS ON PERIDIC TABLE

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