How do you write the alpha decay equation for Lr-256 and the beta decay equation for Sr-90?  

How do you write the alpha decay equation for Lr-256 and the beta decay equation for Sr-90?

 

 

Expert Answers
t-nez eNotes educator| Certified Educator

Alpha decay is the emission of an alpha particle by an atomic nucleus. An alpha particle is a helium nucleus, which contains two protons and two neutrons, and is represented by the symbol

`^4_2 He`

In writing the equation for alpha decay of Lr-256, you need to show the alpha particle as a product. The other decay product will have two fewer neutrons and two fewer protons, which corresponds to Md-252. Here's how to show this is an equation:

`^256_103 Lr-> ^252_101 Md + ^4_2 He`

The sum of masses (superscripts) and the sum of atomic numbers (subsrcipts) must be the same on both sides of the equation.

Beta decay is the emission of a beta particle, which is a high-energy electron. A beta particle is symbolized as follows:

`^0_-1 e`

When an atom undergoes beta decay, a neutron in its nucleus turns into an electron and a proton. The electron is emitted (as a beta particle) and the proton increases the atomic number by one, creating a new element. There is no significant change in mass. The equation for the beta decay of Sr-90 is:

`^90_38 Sr ->^90_39 Y+ ^0_-1 e`

Again, the sums of the mass numbers and atomic numbers do not change.