Posted by Andy on Wednesday, May 12, 2010 at 9:06pm.
# protons = atomic number. Look it up on the periodic table.
#protons + #neutrons = mass number (in this case 81 or 79)
does that narrow it down to 35 prot,79 neutrons and 35 electrons?
Soory bit lost on electrons...
Andy
why was there two choices for mass number???
aha....# of prot and electrons =35 same as atomic number.
#of neutons=mass number - atomic number=44 neutrons...
so 35 protons,44 neutrons and 35 electrons .....hows that???
very good. Why are there two mass numbers? Because the problem tells you Br comes in two flavors; i.e., mass number 79 and 81. But they only asked about the 79 isotope.
thanks...... andy
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