radioactive decay

4

He   = alpha particle (2 neutrons and 2 protons) (a helium nucleus)

2

alpha decay:

219                215                    4              (219-4=215)

    radon     =      polonium  +   He       

86                  84                      2              (86-2=84)

• alpha decay causes the mass and the charge to decrease, as 2 protons and 2 neutrons are released.
• alpha particles are strongly ionisiong but not very penetrating

Beta Decay:

 0

    e     =     beta particle (high speed electron ejected from the nucleus as a neutron turns into a proton)

-1

eg.

14                    14                  0           (14-0=14)

     carbon    =     nitrogen  +    e  

6                       7                  -1           (6--1=6+1=7)

• does not cause the mass of the nucleus to change
• causes the charge of the nucleus to increase, as a proton becomes a neuron
• moderately ionising, moderately penetrating

the emission of gamma ray does not change the mass or charge.

4             = mass number (total number of protons and neutrons)

  He

2             = atomic number (number of protons)

number of electrons= number of protons  

• if an atom loses or gains electrons, it is IONISED.
• atoms of the same element= have the same number of protons but different number of neutrons.

eg.       14                15             13

                  N               N              N

             7                  7               7

• ATOMS ARE POSITIVE IONS WHEN ELECTRONS ARE LOST
• ATOMS ARE NEGATIVE IONS WHEN ELECTRONS ARE GAINED