The answer would be uranium and thorium. When an alpha ejects a particle, it will create a new atom. So, when uranium ejects an alpha particle, it will produce thorium. They call this process as the alpha decay. Alpha decay often happens on atoms that are abundant nuclei such as uranium, radium, and thorium.
Hard question thx for the points
<span>On a very small scale, the numbers of particles of each substance in a reaction are represented by the coefficients in the balanced chemical equation describing the reaction. Hope this answers the question. Have a nice day.</span>