[gwauck]

Hello,

I got a mass defect task at school.
 
230
91

The atomic weight was measured with 235.0 amu.

I always get a negative mass defect.

Is the indication of the measured atomic weight wrong or my way of calculation?


91 protons * 1.007276 = 91.662116000
139 neutrons * 1.008665 = 140.204435000
91 electrons * 0.0005486 = 0.049922600


calculated mass 231.916473600



measured mass (indication) 235.0


mass defect -3.083526400


kg          -5.1202E-27


Energy      -4.61E-10 joules



Thank you for your help.

[Borek]

Your calculations look OK, but result doesn't make sense. There must be something wrong with the 230/91/235 numbers.