What is an atom?
An atom is the smallest particle of a chemical element that can exist while still retaining its chemical properties.
What is the structure of an atom?
Protons and neutrons in nucleus, with electrons shells (at different angels around nucleus) holding electrons.
Features of subatomic particles
Protons: positive charge
Neutrons: no charge
Electrons: negative charge on electron shells
electrons=protons - atom electrically neutral
What is the atomic mass?
Usually decimal at bottom of element picture
= average number of protons + number of neutrons
What is the atomic number?
= number of protons
= number of electrons
John Dalton
- Proposed matter was composed of atoms in 1803
- stated atoms were solid particles without structure
J.J. Thompson
- discovered electrons
- developed plum pudding model of atom
- (positively charged blob with electrons embedded in it)
Ernest Rutherford
- Discovered nucleus
- developed planetary model of atom
- (electrons orbiting central positive nucleus like planets orbiting sun)
Niels Bohr
- proposed electrons occupy stable shells around the central positive nucleus
- realised electrons could move from one energy level to another.
- (electrons in loops around positive protons in nucleus)
James Chadwick
- discovered neutron
- realised neutrons have no charge
- determined approximate mass of neutron
- (electrons in loop around neutron and proton nucleus)
Erwin Schrodinger
- cloud model developed - currently accepted model
- (nucleus surrounded by electron cloud)
Define radiation
The energy given off by a radioactive substance as it breaks down.
Define radioactive
A substance that gives off energy as it breaks down.
What are the main forms of radiation?
- Alpha particles (two protons and two neutrons)
- Beta particles (electrons)
- Gamma rays (high-frequency electromagnetic energy)
How can you be exposed to radiation?
- X-rays
- radiation therapy (eg. for cancer)
- nuclear explosions
- radioactive materials from coal and nuclear power plants
- any radioactive substance
What is an example of a radioactive element?
Technetium:
- Technetium 99m used for medical diagnostic scanning, as it gives off gamma radiation.
- melting point - 2,157 °C
- boiling point - 4,265 °C
- half life - 6 hours
Define half-life
The time taken for half of a radioactive substance to decay.
Describe nuclear fission
Large, unstable atoms break apart into smaller fragments, releasing energy as they do so, causing a chain reaction.
- neutron shot at uranium atom
- uranium breaks apart into barium and krypton and releases kinetic energy, gamma rays and more neutrons, causing a chain reaction.
Uses of radiation in medical industry
- medical diagnostic scans
- sterilisation of medical equipment
- cancer treatment
Uses of radiation in industrial processes
- material density evaluation
- product sterilisation
- quality control
- static elimination
- electricity generation
Benefits and problems with nuclear energy
Benefits:
- increased range of diagnostic procedures
- do things more efficiently and reliably
- does not produce greenhouse gas emissions
- consistent production
- cheap to run
Problems:
- harmful symptoms if exposure occurs (eg. tissue damage, cancer and genetic damage)
- nuclear waste
- expensive to build nuclear power plants
- Nuclear explosions are catastrophic and extremely devastating.
What was the Chernobyl accident? (where, when, what, effects, causes, future)
Where: Nuclear reactor was located near Pripyat, in Ukraine.
When: April 26th, 1986, 1:23am
What: Engineers intended to reduce output but dropped it too quickly. When trying to fix problem, power spiked and reactor overheated. Two explosions occurred causing reactor’s roof to be blown off.
Effects: large amounts of radioactive debris escaped into atmosphere. Firefighters received fatal doses of radiation, and area has remained abandoned ever since. Sharp increase in thyroid cancer as well.
Cause: Flawed reactor design - no large concrete housing and disabling of automatic shutdown mechanisms.
Future: large structure built over site to contain fallout and allow for dismantling of old structure.
What was the Fukushima accident? (where, when, what, effects, future)
Where: Fukushima nuclear power plant #1, in Fukushima, Japan.
When: March 11th, 2011
What: Magnitude 9.0 earthquake occurred off the coast of Japan, triggering an emergency shutdown. Earthquake cause 15metre tsunami, and three cooling systems failed as they’d been damaged by water. Insufficient cooling led to three nuclear meltdowns, chemical explosions and the release of radioactive material.
Effects: Large-scale contamination of sea water and radioactive material widespread across the word. Several areas surrounding reactor were closed down due to high levels of radiation.
Future: Temporary covers over reactor to minimise release of radioactive material. TO prevent entering of groundwater, supercooled salt water pumped through pipes in ground to form a wall of frozen dirt. Robots have been designed to dismantle the reactor.
What are the periods on a periodic table?
1 - hydrogen and helium 2 - lithium, beryllium etc. 3 4 5 6 7
