Radioactivity: Leaving Cert Chemistry

Define radioactivity?

The spontaneous breakdown of unstable nuclei with the emission of one or more types of radiation.

What 3 scientists are responsable for the discovery of radioactivity?

Becquerel, Marie curie and Pierre curie

What are alpha particles?

Are helium nuclei and may be represented as 4 over 2 he 2+

When an element undergoes alpha decay what happenes?

Atomic number decreases by 2 and mass number decreases by 4

What are everyday uses of alpha particle emission?

Americium-241 used in smoke detectors.

What is beta particle?

An electron with a negative charge and greater penetrating ability than an alpha particle.

What changes in the nucleus occur during beta particle emission?

An electron is emitted from the nucleus when a neutron breaks up into a proton and an electron.

What happens during beta decay?

The atomic number increases by 1

What is everyday use I'd beta particle emission?

Carbon dating

What is a radioisotope?

An isotope of an element that emits radiation

What are gamma rays

High energy electromagnetic radiation. They aren't particles and are usually released in conjunction with either alpha or beta particles

What is transmutation?

When an alpha or beta particle is lost of an atom of an element, the element changes into another

What is the use of gamma emission?

Cobalt-60 is used in cancer treatment and to preserve food

What are the differences between chemical and nuclear reactions?

Chemical: cannot change one element to another
Nuclear: elements can be changed into another (transmutation)
Chemical: no changes occurs in the nucleus only the sharing and transferring of electrons
Nuclear: changes occur in the nucleus, e.g the change in the number of protons or neutrons

What is the half-life?

The time taken for half of the nuclei in any given sample to decay

How does carbon dating work?

2 of the isotopes of carbon are carbon 12 and 14. Carbon 14 us a radioactive isotope but carbon 12 isn't. Carbon 14 releases beta particles and has a long half life of 5700 years, when a plant/ animal is living the ration of carbon 12 and 14 is constant. When a plant or animal dies the unstable carbon 14 begins decaying by carbon 12 doesn't change. But the ration between carbon 12 and 14 changes. By measuring the changed ratio with the half life scientists can determine the age of the specimen (carbon dating).