AAMC 9 question - 28

[oms47]

The question goes something like this...

When Be (9,4) is bombarded with deuterons (2,1), a deuteron is absorbed and a neutron is emitted. Which of the following is formed?

So I'm thinking that if a neutron is emitted then we must now have 4 neutrons instead of 5 so I picked choice B which was Be(8,4) however the answer was C Boron (10, 5).

I can see why the atomic number would increase from 4 to 5 but don't understand why the number of total neutrons doesn't change?

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[virtuoso735]

Treat all nuclear decay/capture problems like algebra problems.

Be(9,4) + D(2,1) --> N(1,0) + B(10,5)

You have a total mass of 9+2 on the left, so on the right the mass should be 11 (which is given by 1+10). The charge (protons) should also sum up to the same number on both sides.

When something is emitted, it leaves on the right side. When something is captured or absorbed, it is added on the left side.

 

[oms47]

Thanks that helps!