Answer:
27 amu
Explanation:
The alpha particles is Helium nuclei.
Atomic mass is the sum of the neutrons and protons.
Helium have two protons and two neutrons thus its atomic mass is 4 amu.
₂He⁴
Sodium atom have 12 neutrons and 11 protons. Thus its mass number will be
23 amu.
When it combine with alpha particle it mass will be 27 amu.
23 amu + 4 amu = 27 amu.
Thus new sodium atom have 14 neutrons and 13 protons.
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