Th-234 undergoes beta decay. What is the product nucleus?

Question

Th-234 undergoes beta decay. What is the product nucleus? 

The correct answer is Pa-234

Answer 1

Beta decay is the release of an electron with zero mass and a charge of -1. So mass of product should be same as parent, i.e. 234, but with one additional proton

Th-234 ==> Pa-234