Untitled Flashcards Set

The nucleus is the centre of the atom. It contains protons and neutrons. Protons have a positive charge. Neutrons have a neutral charge. Electrons move in the space outside the nucleus. They have a negative charge. What is an isotope? Atom's with the same number of protons, different number of neutrons. What do the words stable and unstable mean? stable: not going to break down unstable: nucleus going to break down Under what conditions did the nucleus become unstable in the isotops simulation: when there are too many neutrons to protons or too many protons to neutrons ratio is stable-1:1 ratio is unstabke - 5:3 radioisotopes: atoms with unstable nuclei eject particles or electromagnetic waves and undergo nuclear decay. These isotopes are radioactive isotopes (not all isotopes are radioactive) The more extra neutrons it has the more the nucleus is unstable. carbon-12 has 6 protons and 6 neutrons carbon-13 has 6 protons and 7 neutrons carbon-14 has 6 protons and 8 neutrons Types of radioactive decay Alpha and beta decay involve particles Gamma (y) decay is a high energy wave/ray Alpha (a) decay When a nucleus ejects an alpha particle Alpha decay only happens with atoms that have a very heavy nucleus (mass no. of >100) Beta decay is when a nucleus ejects a beta particle a beta particle is equivalent to an electron During beta decay, a neutron has turned into a proton and ejected a b particle (like an electron) You may read about another type of beta decay ejecting a positive electron or a positron Again the mass number has stayed the same but the atom number has changed. But during this beta decay, a proton has turned into a neutron and ejected a positive beta particle (like a positive elctron; a proton) The electromagnetic spectrum is the term used by scientists to describe the entire range of light that exists. From radiowaves to gamma rays, most of the light in the universe, in fact invisible tous High energy radiation (shorter wave lengths), Gamma radiation (high energy, can interact with matter. Only thick lead or concrete can stop these rays. Involvingf freeing electrons. Used in medicine. X rays, HI energy and prenetation power. Made when e-hit a metal surface. Used for making images and cancer treatment. UV lights, found in sunlight. Need bit to make vit D but too much can cause cancer. Can be used to steralize. Visible light blue/purple/red, comes for the son. Made of 7 colours, each has different wave length and frequency. Plants trap the energy in sunlight and turn it into chemical energy- the start of food chains. Infrared radiation - energy as heat from the sun. Can't see it, can feel it. Hotter things emit more infrared radiation. Microwaves, used to radar and communication and cooking. Many substances don't absorb them and metal reflects them. Radiowaves FM/AM, can travel large distances and have long waves. They make electrons in attenae vibrate and this gets converted to waves can bend around the earth's surface. AM signals travel further than FM but are if lower quality and can suffer interference Gamma (y) decay Sometimes protons and neutrons rearrabge inside the nucleus but don't emit a particle. When this happens, harmful, powerful electromagnetic waves called gamma rays are emitted Half-life the rate at which nuclear decay takes place is measured by a radioisotope's half-life. The half-life of a radioisotope is the time it takes for half the nuclei to decay. The radioisotope radon 222 decays into polonium-218 with a half life of 4 days. This means that from 100 radon-222 atoms, 50 would decay over 4 days. Of the remaining 50 nuclei, 25 would decay over the next 4 days. And if you waited another 4 days, only 12 or 15 randon-222 atoms would remain. Biological effects of radiation alpha, beta, and gamma radiation cause damage to the cells of living things because they can enter cells once inside cells radiation can destroy biological molecules and cause unwanted chemical reactions alpha, beta and gamma radiation are called ionizing radiation because they can remove electrons fromn cells/molecules and can cause cell death or cell mutation. Cell death: ionising radiation enters cells and destroys biological molecules, can resullt in radiation burns or radiation sickness Cell mutation: Ionising radiation causes the cell DNA to mutate (slter) without killing the cell, the cell becomes reprogrammed and may become a cancer, increased ionising radiation=increased cell mutation, if gametes are affected then it may cause in herited mutations in off spring. The damage caused by radiation depends on the dose of the radiation (how much exposure-meausured in servies, SV) and the type of radiation Alpha radiation- alpha particles are large, heavy and slow compared to beta particles, 20 times better at ionizing molecules but can only travel a few cm in air, can be blocked by a layer of dead skin or sheet of paper, if isotopes get inside the body and radiate a particles it can be deadly-especially if breathed into the lungs Beta radiation - beta particles are small and fast compared to alpha particles, beta radiation penetrate the skin more deeply than a radiation, can be blocked by a thin plate of alumnium, causes radiation burns to skin and eyes Gamma radiation - gamma radiation is made of electromagnetic waves not particles (no mass and travels fast), y radiation can travel through skin, bone and aluminium- very dangerous, can only be blocked by a very thick layer of concrete or soil or lead