posted by andrew .
Pb --> Bi + ?
Co --> ? + e
I need an explanation on how to find the missing product.
The subscripts must add up on both sides. The superscripts must add up on both sides. For the first one, You start with Pb-210 and end with Bi=210; therefore, the ? particle must have a mass of zero since 210 + 0 on the right = 210 on the left. For the atomic number, you have 82Pb on the left and 83Bi on the right. Therefore, the ? particle must be -1 because 83 + (-1) = 82.
Now, what particle has a mass of zero and a charge of -1? Must be an electron. You replace ? with -1eo