Atoms and Radiation Flashcards
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
What are the groups on the periodic table?
1 2 3 4 5 6 7 8 H Be (lower elements) B C N O F He
Gases and liquids on periodic table
Hydrogen, mercury (Hg), Bromine (Br), Nitrogen, oxygen, fluorine, chlorine and all noble gases
Metals, non-metals and metalloids
Metalloids: Boron, Silicon, Germanium, Arsenic, Antimony, Tellurium
Metals: left of the metalloids (exclud. Hydrogen)
Non-metals: right of metalloids + Hydrogen
Properties of noble gases
- odourless
- colourless
- gases at room temperature
- low reactivity
- low boiling points
Properties of Alkali Metals
Group 1 (exclud. Hydrogen)
- highly reactive
- soft
- metallic
- low density
- low melting points
What group are halogens?
7
Reactivity level increase
Left and down
Electrical conductivity increase
Left and down
Electronegativity trend increase
Right and up
Ionisation energy trend increase
Right and up
Atomic radius trend Increase direction
Down and left
Reactivity trend increase direction
Left and down
Properties of non-metals
- not metallic, often brittle
- not ductile
- usually not lustrous
- variable melting points
- variable state and form
- poor conductors of heat and electricity
Define ion
A charged particle that forms when atoms lose or gain electrons.
What is a cation?
Ions that lose electrons that are positively charged.
What is an anion?
Ions that gain electrons, and become negatively charged.
How do you name ions?
Cations are named after the element (e.g. sodium ion or magnesium ion)
Anions are named by adding ‘ide’ to the stem of the element’s name (e.g. chloride ion, oxide ion)
If a compound contains oxygen (e.g. znSO4), then the second half of the anion become ‘ate’. (e.g. Zinc Sulfate)
What is valency?
The valency is the number of atoms an atom will lose or gain to form an ion and fill the outer shell. This shell is known as the valency shell.
What was the contribution of Dmitri Mendeleev in developing the Periodic Table?
He was a Russian chemist, credited with publishing the periodic table. He arranged the elements known at the time in order of relative atomic mass.
Who was Alexandre-Emile Béguyer de Chancourtois?
French Geologist and mineralogist who was the first to arrange the chemical elements in order of atomic weights.
Who was Julius Lothar Meyer?
German chemist who published his version of the periodic table with elements arranged with similar chemical and physical properties.
Who was Henry Moseley?
English physicist who used x-ray technology to determine the atomic number of each element and justified the elements on the periodic table.
What are the origin of the chemical symbols for the following elements: mercury, sodium, potassium, tungsten, tin
Mercury: Hg derives from the Latin ‘hydrargyrum’
Sodium: Na derives from the Latin for ‘natron’
Potassium: K comes from the Latin, ‘kalium’
Tungsten: W symbol from its German name Wolfram (Wolframite was the ore it was found in)
Tin: Sn comes from the Latin word ‘stannum’
How to graph half-life
How much of substance remaining on vertical axis
Time on horizontal axis
