I believe it's 6789 times 10^4. I could be wrong, due to the fact that I don't remember what's the definition of the scientific notion. I hope this helps, or at least gives you an idea! :D
Answer:
Uranium-238 undergoes alpha decay to form Thorium-234 as daughter product.
Explanation:
Alpha decay is indicative of loss of the equivalents of a helium particle emission. The reaction equation for this reaction is shown below:
→ 
I hope this explanation is clear and explanatory.
K is Potassium
Cl is Chlorine
There are 2 elements.