…AND THE AVERAGE ATOMIC MASS

Isotopes

PG 88 GENERAL- ATOMS OF THE SAME ELEMENT BUT HAVE DIFFERENT AMOUNTS OF NEUTRONS IN THE NUCLEUS PAGE 54 PRE AP ATOMS WITH SAME NUMBER OF PROTONS BUT DIFFERENT NUMBERS OF NEUTRONS

Isotopes

EACH ISOTOPE HAS A DIFFERENT MASS DUE TO THE

DIFFERENT AMOUNTS OF NEUTRONS IN THE NUCLEUS.

WE CAN NOT LIST EVERY ISOTOPE ON THE PERIODIC TABLE SO WE HAVE HAD TO

TAKE THE AVERAGE WEIGHTED MASS TO DISPLAY

Mass is affected.

TO FIGURE THE AVERAGE MASS THAT IS LOCATED ON THE PERIODIC TABLE

ONE MUST-LIST THE ISOTOPES AND THEIR

PERCENTAGE OF ABUNDANCE-MULTIPLY EACH % BY THAT ISOTOPES

MASS AND DIVIDE BY 100 TO GET THAT ISOTOPES RELATIVE MASS

-FINALLY ADD THE RELATIVE MASSES FROM ALL ISOTOPES TOGETHER TO GET THE AVERAGE WEIGHTED MASS

FOR THAT ELEMENT

How is average weighted mass figured?

PURE CARBON CARBON-12 IS 98%

CARBON-13 IS 1.11%THE MASS OF CARBON 12 IS

12.000AMUTHE MASS OF CARBON 13 IS 13.004

C12=(12.000X98%)/100+

C13 (13.004X 1.11%)/100=11.76 +.1443=11.90 (12)

Example