Posted by Shannon on .
Write a balanced nuclear equation for the positron emission of each of the following nuclei: a) arsenic74
b) oxygen15

Chemistry 
DrBob222,
The secret to these is to write an equation in which the subscripts add up on both sides and the superscripts add up on both sides. Subscripts and superscripts are a problem on the board so this is the way I will show it.
8O15 means oxygen with an atomic number of 8 and a mass of 15
33As74 means As with an atomic number of 33 and a mass of 74
A positron is the same as an elecrron but with a positive charge so we write it as 1e0.
8O15 ==> 1e0 + X
So 8 on the reactant side = 1 + something on the product side. What is something? That must be 7 because 7+1 on the product side = 8 on the reactant side.
What about the superscripts; i.e., the numbers on the right. 15 on the reactant side = 0 on the product side + something. That something must be 15 because 15+0 = 15. Now what is element X? The atomic number is 7 so that makes it N. Look at the periodic table to confirm that.