Question

A certain radioactive atom has 90 protons and 142 neutrons. If this atom undergoes alpha decay, what is the mass number of the daughter atom? The mass number of the daughter atom is .

Answer 1

Correct Answer: 228

Step-by-step explanation:

alpha decay is removing alpha particle

2 number of protons, 4 mass number = 2 protons + 2 neutrons

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We have:

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90 protons and 142 neutrons

- 2 protons - 2 neutrons

88 protons 140 neutrons

Mass number of new (daughter) atom = 88 +140 = 228

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Answer 2

228

Step-by-step explanation:

alpha decay is removing alpha particle
`_2^(4)He`

2 number of protons, 4 mass number = 2 protons + 2 neutrons

We have

90 protons and 142 neutrons

- 2 protons - 2 neutrons

88 protons 140 neutrons

Mass number of new (daughter) atom = 88 +140 = 228