Nuclear Radiation Flashcards
Radioactive decay -
Stable nuclei
An atoms nucleus can only be stable if it has a certain number of neutrons for the number of protons it has.
Elements with fewer protons, such as the ones near the top of the periodic table, are stable if they have the same number of neutrons and protons, for example carbon, carbon-12 is stable and has six protons and six neutrons.
Types of radioactive decay
An unstable nucleus can decay by emitting an alpha particle, a ß- (beta minus) particle, a ß+ (positron), a gamma ray or in some cases a single neutron.
Alpha particle
If the nucleus is unstably large, it will emit a ‘package’ of two protons and two neutrons called an alpha particle.
An alpha particle is also a helium-4 nucleus, so it is written as 42He. It is also sometimes written as 42α.
Alpha decay causes the mass number of the nucleus to decrease by four and the atomic number of the nucleus to decrease by two.
Beta minus decay
If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron. This electron is called a beta minus (β-) particle - this process is known as beta radiation.
A beta particle has a relative mass of zero, so its mass number is zero. As the beta particle is an electron, it can be written as 0-1e. However, sometimes it is also written as 0-1β.
The beta particle is an electron but it has come from the nucleus, not the outside of the atom.
Positron (ß+) emission
If the nucleus has too few neutrons, a proton will turn into a neutron and emit a fast-moving positron. This positron can be called a beta plus (β+) particle - this process is known as positron emission.
A positron is the antimatter version of an electron. It has the same relative mass of zero, so its mass number is zero, but a +1 relative charge. It can be written as 0+1e, however sometimes it is also written as 0+1β.
