KaplanBB:pg12 Qs :about Radioactive Beta Decay

[A6project]

Hi, as I go over Gen Chem parts, I struggle to understand the explanation.

It is on page 310. This is an example of B radioactive decay question.

in the middle part, it states, " 27 = Z' - 1 "

I don't understand why it is -, instead of positive.

And I couldn't figure out this example is whether beta-negative or beta-positive decay.

Plzzzz HELPPP!!!! Thanks in advance!!!

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[afsheen21]

Hey, so I'll try to help the best i can.
So for Alpha decay you use the formula
A daughter= A parent - 4
Z daughter= Z parent- 2

For B- decay you use the formula
A daughter=A parent
Z daughter= Z parent + 1
(this is because a neutron is dissapearing and a proton takes it place, hence the +1 and so the mass number is unchanged but the atomic number is increased by 1)

For B+ decay (positron)
A daughter= A parent
Z daughter= Z parent - 1
this splits a proton into a positron and a neutron. Atomic number decreased by 1.

I hope this helps!

 

[herkulease]

I ahd to flip through my book to find it.

but this is negative beta decay.

It is because that's you emitted a electron.

the Z' represents the atomic number of the daughter.

The -1 comes from the fact it is a negative beta decay.

You can write it as an addition problem if you like. But you just have to remember that what you emitted had an electron.

Z' + (-1) is the same as Z' - 1

It is easier at least to me to think of it as an addition problem.

Parent = Daughter + Energy.

As long as you remember what amounts to the mass and atomic number for each decay you'll be set.