1.3 NUCLEAR DECAY AND RADIATION Knowledge of subatomic particles has led to many advancements- unfortunately besides the advancements in power plants there has been costs-nuclear warfare and waste

Nuclear Decay The nucleus-cluster of protons and neutrons-is in the centre of an atom It doesn’t stand still! ?(a bit like some year nines!!!!) The particles are constantly moving- vibrating, rotating and re-arranging This causes some to emit electromagnetic radiation- called Gamma rays Sometimes particles are emitted at high speed This is called : a nuclear reaction or nuclear decay During this process atoms can change from one element to another-transmutation Can only happen in nuclear decay

examples Sodium Na – which is a metal can decay to form the Noble gas Neon Ne Soft metal can be cut at RM temp Neon- gas- emits a single wavelength of light but if the glass is coloured the gas appears in different colours –needs electric current to pass through

Radio-isotopes Most atoms are stable- have stable nuclei- do not ever decay Some (a tiny amount) do decay- as they are said to be unstable They eject particles at any minute Unstable atoms = radioisotopes

Radioactive ! Any atom may have many isotopes if you remember- only some of those isotopes will be radioactive Three types of Nuclear Deca y Alpha Decay: Nucleus ejects an alpha particle Two protons and two neutrons Only happens in atoms with heavy nuclei- mass numbers greater than 100 i.e. Uranium- mass no. 238 Losing the protons changes the atomic number therefore it is a new element/different element

Beta Decay: Nucleus ejects beta particles which are-identical to electrons and have negative charges Beta decay involves a neutron being converted to a proton Increases atomic number by 1- again a new element is formed Mass number stays the same

Gamma Decay Sometimes protons and neutrons rearrange their position in the nucleus No particles are emitted Instead a wave of electromagnetic radiation is emitted- a GAMMA ray Hence Gamma decay-like X rays but more powerful

Half Life : do skittle prac pg 31formative The rate at which the decay happens is measured by a radioisotopes half life. Half life is the time it takes for half of the nuclei to decay E.g radon 222, a radioactive isotope decays to another element polonium 218 with a half life of 4 days This means 100 atoms of radon 222 in 4 days 50 would decay, then the next 4 days 25 more would decay and then 12 more over the next 4 days AND so on till total decay. Half lives vary from a fraction of a second to millions of years!!!

Carbon Dating Understanding the half life of radioisotopes has helped archaeologists

The half life of carbon-14 is used to date the age of fossils- we look at this in more depth in term 4 Carbon is in all living things The amount is constant throughout the lifetime of the plant or animal as it is constantly absorbed through the air and food When something dies- can’t absorb anymore-so the carbon in the “body’ decays to form nitrogen with a half life of 5730 years This means they look at how much carbon remains in an animal/fossil etc or plant and determine how long ago it lived

Radiation Nuclear radiation:-means any rays or particles emitted by atomic nuclei Includes the alpha, beta and gamma particles/rays already discussed Is quite harmful to living things But also useful in medicine, and industry

Biological effects of radiation Once inside a cell- unwanted chemical reactions can occur They remove electrons from other atoms and molecules Cells mutate or die The cell dies when molecules are damaged beyond repair- radiation burns or radiation sickness occurs The effects can take a while to appear The radiation sickness symptoms include: nausea, vomiting, fever, hair loss and diarrhoea

Radiation burns

Cell mutation: Cell mutation happens when the DNA is damaged but the cell doesn’t die DNA has all the genetic instructions to make you who you are- it tells all the cells how to function properly Damaged DNA means reprogramming occurs- the instructions are changed= usually means the cell is uncontrolled and cancer occurs Some mutations are inherited or passed down if they occur in egg and sperm cells

DOSE Radiation is harmful if you are exposed to large amounts or a big “DOSE” Radiation doses are measured in Sieverts -1 Sievert or Sv is a large dose that will cause radiation sickness Scientists generally measure in smaller doses called micro Sieverts Pg 25 (P) ALPHA RADIATION: large particles doesn’t travel far CAN BE HANDLED QUITE SAFELY Is fatal if Alpha particles do get in the body

Beta Radiation Small. Fast particles Penetrates skin deeply More likely to cause radiation burns Easily blocked though with thin sheets of aluminium GAMMA Radiation: Travels through bone, skin and aluminium Very dangerous to humans Need lead or concrete to block the rays

Useful radiation When handled safely is useful in medical treatments and diagnosis, industrial applications and scientific research Used to treat Cancer-radiotherapy Cancers are given high doses of radiation-kills cancer cells but hopefully not too many normal cells Can irritate the skin Cause burns Ulcers Swellings Nausea and hair loss Heart disease and other cancers!

radioisotopes Used in medical diagnoses Used to give images of internal organs Called nuclear medicine or imaging Radioisotopes are injected into the body they collect in organs and emit low levels of radiation that can be detected outside the body to display an image

Industrial- Used in sterilisation techniques of equipment Used for bandages and needles to kill bacteria onm them and make them sterile Can be used like x –rays on humans to look inside things like minerals, looking for gas and iol and water Some smoke detectors used radiation to tell us if smoke is around