If an atom of sodium combines with (captures) an alpha particle that has 2 protons and 2 neutrons, its new mass number will be
a)
13 amu
b)
15 amu
c)
25 amu
d)
27 amu

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.

i do not get it   at all