Write a balanced equation for:

Question

1. beta decay of iodine-138
2. capture of an electron by cadmium-104

Answer 1

It is difficult in this forum for us to write subscripts and superscripts. Here is what I'll do. The number to the left of the element symbol is the atomic number. The number to the right of the element symbol is the mass number. The way you do these problems is to make the subscripts and superscripts on EACH side add to the same value.In this case, you want the left numbers on both sides to add up and you want the right numbers to add up on both sides.

53I2138 ==> -1e0 + 54Y138
You know the beta particle is an electron (-1e0) so you write Y for the element that is left. Adding up subscripts on both sides you have 53 on the left and -1 on the right; therefore, the atomic number for Y MUST be 54 since -1 + x = 53 so x must be 54. Look on the periodic table and see what 54 is. That's Xe so replace Y with Xe. The superscript must be 138. The complete equation is
53I2138 --> -1e0 + 54Xe138

Now you do the last one.