Everything Science Grade 11

CHAPTER 4. ATOMICNUCLEI 4.3

See video: VPhyr at http://www.everythingscience.co.za

Example 1: Radioactive decay

QUESTION

The isotope^24195 Am undergoes radioactive decay and loses twoalpha particles.

1. Write the chemical formula of the element that is produced as a result of the decay.


2. Write an equation for this decay process.

SOLUTION

Step 1 : Work out the numberof protons and/or neutrons that the radioisotope loses

during radioactive decay

One α particle consists of twoprotons and two neutrons. Since two α particles

are released, the total number of protons lost is four and the total number of

neutrons lost is also four.

Step 2 : Calculate the atomic number (Z) and atomic mass number (A) of the element

that is formed.

Z = 95− 4 = 91

A = 241− 8 = 233

Step 3 : Refer to the periodic table to see which element has the atomic number that

you have calculated.

The element that has Z= 91 is protactinium (Pa).

Step 4 : Write the symbol forthe element that has formed as a result of radioactive

decay.

233

91 Pa

Step 5 : Write an equation for the decay process.

241

95 Am→

233

91 Pa + 4 protons + 4 neutrons