P4 - Atomic Structure

How did the model of the atom develop?

* 1800s: Dalton model - spheres
* 1900s: JJ Thompson - plum pudding
* Rutherford’s alpha particle experiment
* Bohr - discovers shells
* Chadwick - neutrons - nuclear model

Def: isotope

a version of an element with different number of neutrons

What happens to unstable isotopes?

decay into other elements, give out radiation

Def: alpha particle

* 2 neutrons, 2 protons
* ionising
* stopped by paper

Def: beta particle

* 1 electron
* fast moving
* moderately ionising
* stopped by perspex

Def: gamma ray

* wave of electromagnetic radiation
* weakly ionising
* stopped by lead

Def: half life

time taken for number of radioactive nuclei in an isotope to halve

How can you measure radiation?

Geiger-Muller tube and counter

What is the unit for radiation?

becquerels (Bq)

What are the dangers of a short half lives?

nuclei rapidly decay, high levels of radiation emitted quickly before becoming stable

What are the dangers of long half lives?

expose areas to small amount of radiation but regularly and over a long time

Def: irradiation

exposure to radiation

What are the risks of irradiation?

* tissue damage
* cancer
* radiation sickness

How is radiation used in medicine?

* medical tracers
* radiotherapy

Def: medical tracer

isotopes with short half lives injected and their progress can be followed by an external detector to monitor to look at tissues

Def: radiotherapy

can kill cancer cells

What are the 2 types of radiotherapy?

* gamma rays directed at tumour
* beta-emitters implanted next to tumour

Pros of radiation therapy

* can diagnose cancer
* can treat cancer

Cons of radiation therapy

* long term exposure dangerous
* side effects