On the weekend, a tank of radioactive material leaked from the closed Ranger uranium mine in the Northern Territory. Radioactivity and radiation are often used interchangeably, but they describe different yet related processes.
An atom is the smallest particle that can be described as a chemical. At the centre of each atom is a nucleus , containing a number of protons positively charged particles.
The number of protons determines what chemical the atom is. All carbon nuclei contain six protons — it is what defines them as carbon nuclei.
Five protons would be a boron atom, seven protons a nitrogen atom. The nucleus also contains a number of neutrons particle with no charge. Atoms of the same chemical can have different numbers of neutrons. Some carbon atoms have more or fewer neutrons — seven neutrons makes carbon and eight for carbon The nuclei of carbon and carbon are stable, but carbon is radioactive and is the basis of radiocarbon dating.
Atoms of the same chemical with different numbers of neutrons are known as isotopes. Surrounding the nucleus are very small negatively charged particles called electrons. These are held in place called orbitals by their attraction to the positively charged nucleus.
An atom contains as many electrons as protons. Adding or removing an electron from the atom results in a charged particle, called an ion. Ions can react very differently to atoms. A chlorine atom is very reactive and dangerous; a chloride ion is part of table salt. This becomes important when talking about ionising radiation later. Decay occurs naturally and spontaneously to unstable nuclei. This instability is usually caused by a mismatch between the number of protons and neutrons.
Neutron release, alpha and beta decay are all accompanied by the release of a particle. All of those that land heads are thrown away. By the law of averages, we should have 2, coins half remaining. If we then take another minute to flip all of those coins and discard the heads, we will be left with 1, coins.
And again, taking another minute to flip the 1, coins, we will be left with coins. The half-life of an isotope is the same for all nuclei of that type all carbon nuclei have a half-life of about 5, years and all carbon nuclei have a half life of about 2. If we perform the coin flip ten times we will be left with four coins — one thousandth of the starting number.
This is important because it is considered that after ten half-lives there is a negligible amount of material remaining. As we have seen, radioactive decay is a property of a particular nucleus.
JavaScript appears to be disabled on this computer. Please click here to see any active alerts. Estimate your yearly dose from the most common sources of ionizing radiation with this interactive online dose calculator.
Radiation is energy. It can come from unstable atoms that undergo radioactive decay , or it can be produced by machines. Radiation travels from its source in the form of energy waves or energized particles. There are different forms of radiation and they have different properties and effects.
Non-ionizing radiation has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove electrons from atoms. Examples of this kind of radiation are radio waves, visible light and microwaves. Ionizing radiation has so much energy it can knock electrons out of atoms, a process known as ionization. Ionizing radiation can affect the atoms in living things, so it poses a health risk by damaging tissue and DNA in genes. Ionizing radiation comes from x-ray machines, cosmic particles from outer space and radioactive elements.
Radioactive elements emit ionizing radiation as their atoms undergo radioactive decay. Radioactive decay is the emission of energy in the form of ionizing radiation ionizing radiation Radiation with so much energy it can knock electrons out of atoms. The ionizing radiation that is emitted can include alpha particles alpha particles A form of particulate ionizing radiation made up of two neutrons and two protons. Alpha particles pose no direct or external radiation threat; however, they can pose a serious health threat if ingested or inhaled.
Some beta particles are capable of penetrating the skin and causing damage such as skin burns. Beta-emitters are most hazardous when they are inhaled or swallowed.
Gamma rays can pass completely through the human body; as they pass through, they can cause damage to tissue and DNA. Radioactive decay occurs in unstable atoms called radionuclides. The energy of the radiation shown on the spectrum below increases from left to right as the frequency rises. Other agencies regulate the non-ionizing radiation that is emitted by electrical devices such as radio transmitters or cell phones See: Radiation Resources Outside of EPA.
Alpha particles come from the decay of the heaviest radioactive elements, such as uranium , radium and polonium. Even though alpha particles are very energetic, they are so heavy that they use up their energy over short distances and are unable to travel very far from the atom.
The health effect from exposure to alpha particles depends greatly on how a person is exposed. Alpha particles lack the energy to penetrate even the outer layer of skin, so exposure to the outside of the body is not a major concern.
Inside the body, however, they can be very harmful. If alpha-emitters are inhaled, swallowed, or get into the body through a cut, the alpha particles can damage sensitive living tissue. The way these large, heavy particles cause damage makes them more dangerous than other types of radiation. The ionizations they cause are very close together - they can release all their energy in a few cells.
This results in more severe damage to cells and DNA. These particles are emitted by certain unstable atoms such as hydrogen-3 tritium , carbon and strontium Beta particles are more penetrating than alpha particles, but are less damaging to living tissue and DNA because the ionizations they produce are more widely spaced.
They travel farther in air than alpha particles, but can be stopped by a layer of clothing or by a thin layer of a substance such as aluminum.
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