Ch.3-Radioactivity Flashcards
-Americium-241, Carbon-14 and Cobalt-60 decay formula.
What is radioactivity?
Radioactivity is the spontaneous decay of certain unstable nuclei, accompanied by the emission of radiation.
What did Henri Becquerel do?
Becquerel discovered radioactivity by noticing that uranium salts caused shadows to appear on photographic plates.
What did Marie and Pierre Curie do?
Marie Curie named the emission of radiation radioactivity. They discovered that ore pitchblende contained not only uranium, but 2 other elements, which they named polonium and radium which are far more radioactive.
What are the 3 types of radiation?
Alpha particles(+), Beta particles(-) and gamma rays(neutral).
What is the Geiger-Muller tube?
A Geiger-Muller tube is used to detect radioactivity. In it, a gas is ionised by alpha, beta or gamma radiation, and the resulting electric current is amplified and detected.
What are alpha particles?
Alpha particles consist of 2 protons and 2 neutrons (identical to helium nuclei). They move relatively slowly and can be stopped by human skin or a few sheets of paper. They are strongly ionising and hazardous if inhaled. Americium-241 is an alpha particle emitter, found in smoke detectors.
What are beta particles?
Beta particles are electrons, with a negative charge and greater penetrating ability than alpha particles. They can be stopped by 5mm of aluminium. Carbon-14 emits beta particles and is used in radiocarbon dating.
What are gamma rays?
Gamma rays are high-energy electromagnetic radiation, with greater penetrating ability than beta particles. They have no mass and no charge. Cobalt-60 is a gamma ray emitter, used for cancer treatment.
Distinguish between chemical and nuclear reactions.
In chemical reaction, there is no elemental change, whereas there’s a change in element in nuclear reaction. Chemical reactions involve electrons, while nuclear reactions involves nucleus. Nuclear reactions release nuclear energy, unlike chemical reaction. In chemical reaction, bonds are broken and formed, in nuclear reactions, no bonds are broken or formed.
What happens when an isotope undergoes alpha and beta decay?
When an isotope undergoes alpha decay, its atomic number decreases by 2, while it’s mass number decreases by 4. When an isotope undergoes beta decay, its atomic number increases by one, while the mass number remains unchanged.
What is a radioisotope and what is meant by its half-life?
Radioisotopes are unstable, radioactive isotopes. The half-life of a radioisotope is the time taken for half of the atoms in a sample of the isotope to decay.
What is background radiation and give examples.
A low-level of ionising radiation surrounds us at all times. The sources include nuclear waste, fallout from weapons test, medical sources, cosmic rays, food and drink, rocks and soil and radon gas.
What is radiocarbon dating?
Radiocarbon dating is a technique used to find the age of an object containing carbon. It is based on the ratio of 14C to 12C in the object.
What is a nuclear reaction?
A nuclear reaction is a process that alters the structure of an atomic nucleus.
What is a chemical reaction?
Chemical reactions involves the transfer of electrons.
