Physics P2.6

P2 6.1

Nuclei of radioactive substances becomes stable by radioactively decaying. This happens by emitting radiation to become other elements. The three main types of radiation are alpha, beta and gamma radiation. It is very hard to tell when an unstable nucleus will decay, because it is a random process and has no factors working on it.

However, background radiation exists all around us all of the time: from the environment, space and devices such as x-ray tubes.

P2 6.2

Atoms were to have been thought of like plum pudding and that electrons were scattered throughout the positively charged atom. This was called the 'plum pudding model'.

Then Rutherford, Geiger and Marsden made an alpha particle scattering experiment, where they fired alpha particles at a gold sheet. A few things happened which helped us infer things about atoms:

• Most of the alpha particles passed through, suggesting that most of an atom is empty space.
• Some of the alpha particles reflected, suggesting that the nucleus has a positive charge.
• A few rebounded at large angles, suggesting that the nucleus had a large mass and a large positive charge.

P2 6.3

In alpha radiation, the nucleus loses two protons and two neutrons and emits them. In beta radiation, a neutron is changed into a electron and a proton, then the electron is emitted.

An atom which has the same amount of protons and the same amount of electrons are regular atoms, anytime that they are different, it is an ion.

However, atoms of the same element but different number of neutrons is an isotope.

Protons + neutrons = mass number!

An alpha particle consists of two protons and two neutrons, therefore its mass number is 4 and…