7.1 Atoms and radiation Flashcards
Which French physicist discovered the image of a key on a photographic film he developed and when
Henri Becquerel, 1896
What did Henri Becquerel discover about uranium thanks to the photographic film
- the film was in a drawer, under a key. On top of that there was a packet of uranium salts
- he realised the uranium salts must have sent out some form of radiation that passed through paper but not metal
What did Marie Curie discover
- uranium salts emitted radiation, she described that uranium was radioactive
- she and her husband discovered new radioactive elements and named of them polonium
What test did Rutherford do and what did he discover
- he put different materials between the radioactive substance and the detector
- he discovered that alpha radiation was stopped by paper and that beta radiation went through paper
What third type of radiation did scientists later discover
Gamma radiation (even more penetrating than beta)
Alpha radiation def
Alpha particles, each composed of two protons and two neutrons, emitted by unstable nuclei
Beta radiation def
Beta particles that are high-energy electrons created in, and emitted from, unstable nuclei
Gamma radiation def
Electromagnetic radiation emitted from unstable nuclei in radioactive substances
Who invented the Geiger counter
Hans Geiger, Rutherford’s research student
What did Rutherford go on to propose after he discovered the nucleus
That the nucleus contained protons and neutrons
Why are some substances radioactive
- atoms of a radioactive substance have an unstable nucleus
- an unstable nucleus becomes stable (or less unstable) by emitting alpha, beta or gamma radiation
- it is a random event
What is it called when an unstable nucleus emits radiation
Decay
