It an atom emits an alpha particle the atomic number of that will ___ by 2 and the mass number will drop by __ Explain why this happens? Chemistry 1 Answer Dimri · Nam D. Feb 26, 2018 Atomic Number will decrease by #2# and the mass number will drop by 4. Explanation: If #""_Z^AX# be the parent nucleus and #Y# be the daughter nucleus, then nuclear equation of emission of alpha particle will be: #""_Z^AX -> ""_2^4He + ""_(Z-2)^(A-4)Y# Answer link Related questions How do I determine the molecular shape of a molecule? What is the lewis structure for co2? What is the lewis structure for hcn? How is vsepr used to classify molecules? What are the units used for the ideal gas law? How does Charle's law relate to breathing? What is the ideal gas law constant? How do you calculate the ideal gas law constant? How do you find density in the ideal gas law? Does ideal gas law apply to liquids? Impact of this question 919 views around the world You can reuse this answer Creative Commons License