Final answer:
The product of alpha emission from radium-224 (Ra-224) is radon-222 (Rn-222), which occurs due to the loss of an alpha particle resulting in a decrease of 4 in mass number and 2 in atomic number.
Step-by-step explanation:
The product of alpha emission from the radioactive isotope radium-224 (Ra-224) is radon-222 (Rn-222). Alpha emission involves the release of an alpha particle, which is a helium nucleus consisting of 2 protons and 2 neutrons. Due to this emission, the original atom loses 4 in mass number and 2 in atomic number. For radium-224, which has an atomic number of 88, alpha emission will decrease the atomic number to 86, making the daughter element radon-222. This is because alpha decay leads to a reduction by 4 in mass number (from 224 to 220) and by 2 in atomic number (from 88 to 86), leading us to the correct answer of (B) Radon-222 (Rn-222).