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In this video, I will show you how to solve for the missing isotope.
Let's use this constructed response question from the August 2010 chemistry regents exam.
When referring to the answer booklet, you will see the following incomplete equation.
Your job is to complete it by writing a notation for the missing nuclide, or isotope.
In order to do this, you should know that the numbers on the top are called mass numbers
representing the mass and the numbers on the bottom are called atomic numbers representing
the charge. This is important because the mass before
MUST equal the mass after, which means that 4 plus 206 must equal 210 on the other side,
or before the arrow. Likewise, the charge before must equal the
charge after, so that 2 plus 82 must equal 84 before the arrow.
Finally, to find the missing symbol, simply look up atomic number 84 in the periodic table
of elements and you will find your answer. Now, the Chemistry Regents has a tendency
to use the same questions over and over again, sometimes word for word and often times, right
around the same question numbers, like this one from the June, 2011 Chemistry Regents
exam! Considering they used the same exact example,
can you guess what the answer will be? .... And that's because the mass before must equal
the mass after and the charge before must equal the charge after with 82 being the atomic
number for Pb, which is lead. But even if they decide to change the letters
and number around on you, like they did here with another question numbered 84 from the
January, 2012 Chemistry Regents , the rules for mass and charge still apply.
So, 60 before needs to equal 60 after and 27 = -1 plus 28 and not 26 like most students
tend to think. As for the symbol, 28 is the atomic number
for nickel which completes the notation for the missing product.
Please take a moment to subscribe to my channel if you haven't already and if you are interested
in seeing more patterns, tips and tricks regarding the chemistry regents, make sure to watch
"100 Ways to Pass the Chemistry Regents!"