Atoms Flashcards
What does half-life mean?
The half-life of a radioisotope is the amount of time it takes a radioactive isotope to decay to half its original value.
What does radioactive decay mean?
the process where an unstable atom loses energy through radiation. These can be emitted through alpha, beta and gamma rays.
Sub-atomic Particles
neutrons, protons and electrons
Name the charge of sub-atomic particles
Neutrons - neutral
Protons - positive
Electrons - negative
What is a nucleus
A nucleus is the centre of an atom and contains protons and neutrons. These particles are held together through very strong forces.
What is an isotope?
An isotope is an atom of the same element that differs in the number of neutrons, hence affecting its total mass.
What is the atomic number?
The atomic number is found on the bottom left-hand side of the element symbol and indicates its number of protons and electrons.
What is the mass number?
The mass number is the sum of the protons and neutrons in the nucleus and is indicated on the top left-hand side of the elemental symbol
What are protons?
Protons are positively charged particles found in the nucleus of an atom
What are neutrons?
neutrons are particles with no electrical charge that are found in the nucleus of an atom
What are electrons?
Electrons are negatively charged particles that orbit the nucleus in shells. The further shell they are in = the more energy they have. Electrons are very light and move aorund very quickly.
What are valence electrons?
Valence electrons are electrons found in the outermost shell. These valence electrons contain the most energy
Draw and label a diagram of an atom
List the number of protons, electrons and neutrons using the lithium atom. This atom has an atomic mass of 6.941 and a atomic number of 3.
Lithium has 3 protons, 3 electrons and 3.941 neutrons.
What process do particle equations represent?
Radioactive decay
During radioactive decay mass or charge can…..
neither be created nor destroyed
What must the total mass of particles equal after nuclear decay?
The sum of the masses of the particles before the nuclear decay
What type of decay has occurred if the mass is the same but the atomic number increases?
Beta decay has occurred and an electron has been added.
what are alpha particles?
positively charged helium atoms, consisting of 2 protons and 2 neutrons, cannot travel easily through materials and can be stopped by a sheet of paper or human skin. pose little damage to humans but can cause damage through inhalation, injection or digestion
If helium has been added to another atom what type of decay has occured?
alpha radiation
What are beta particles?
can have a positive or negative charge and travel at high speeds. can penetrate human skin but not plastic wood or aluminium
What is the symbol for alpha, beta and gamma?
α, β, γ
What are gamma rays?
Gamma rays are not particles but bursts of energy released after alpha or beta particles are emitted. Can cause serious damage and can be stopped through a thick layer of concrete
How many days will it take for tritium to fall to a quarter of its origianl mass. The half life of 100g of tritium is 4500 days.
So, it takes 4500 days to reach 50 grams. Which is half, so if we half again to reach a quarter (25g) we get 9000 days to reach a quarter of its original mass.
Why is radiation helpful/useful?
Radiotherapy uses radioisotopes or X-rays to kill cancer cells or prevent them from multiplying. Radioactive substances can also be inserted into the body to detect the cause of disease. Body scans can also be performed through the manipulation of gamma rays to obtain images of the parts of the body inside. Gamma rays can also be exposed to foods to help prevent them from spoliing.
External radiotherapy, internal radiotherapy/brachytherapy
External radiotherapy - cancer treatment where radiation is directly applied from an external machine to the site of cancer
Internal Radiotherapy/Brachytherapy - Radioisotopes are placed inside the body, near, or at the cancer
What are the dark side of radioactivity?
High levels of energy from nuclear reactors can cause serious, injury, disease or death and can pose a significant risk to your health.
Nuclear weapons, when detonated, release enormous amounts of heat and radiation which spread out from the centre of the blast known as ground zero. This emmision of heat and radiation is known as thermal flash.
Any mass amounts of energy can contaminate produce, soil, milk and will eventually result in human ingestion.
What is nuclear fallout?
Nuclear fallout is when the residue and irritated particles begin to come back dowwn to Earth, a few weeks after a nuclear explosion.
Postive Ion
when there are more protons in the nucleus
Negative Ion
when there are more electrons than protons
Neutral atom
all protons and electrons are equal and the neutrons summed with protons is equal to the mass number
What type of radiation is least ionising?
Gamma radiation because it won’t easily strip electrons from other atoms.
What determines the motion of particles in matter?
Energy
Where do controlled fission reactions occur
Nuclear Power Plants
What happens in beta radiation?
In this particular radiation, one of the neutrons in the nucleus splits up into a proton and anelectron. The proton stays with the atom changing the atomic number. The electron is emitted from the nucleus, and becomes the emitted beta particle.
What term describes a atom joined wityh 2 or more other atoms?
Molecule
What are changes in state?
Physical changes that do not change the chemical composition.
What is matter composed of?
particles
What radiation is good for sterilising equipment?
Beta radiation is good for hygiene as it kills bacteria
What does Bohr’s model present?
that electrons orbit in energy levels.
How are elements arranged by?
Increasing atomic number
Instrument used to detect radioactcivity
geiger counter
When does radioactive decay occur?
when the nucleus of an atom is unstable
How is relative molecular mass calculated
through adding the relative atomic masses of each atom in the molecule
Electric charge of a alpha particle
+2
