Atomic structure

• What is the radius an atom? 1x10-10 metres
• What do atoms contain? [2] - Positively charged nucleus made up of protons and neutrons - Surrounded by negatively charged electrons
• When will the energy level of an electron change? When the atom emits or absorbs electromagnetic radiation
• What happens when a metal atom loses one of its outer electrons? It becomes a positive ion.
• What happens when an atom gains an electron. It becomes a negative ion.
• What does all atoms of a particular element have the same number of? Same number of protons
• What is the atomic number? The number of protons in an atom of an element.
• What is the total number of protons and neutrons in an atom called? Atomic mass number
• What are isotopes? Atoms that have different numbers of neutrons.
• Who discovered the electron? J.J Thompson
• When did J.J Thompson discover the electron? 1897
• Who carried out the rutherford experiment? Geiger and Marsden
• When was the Rutherford experiment carried out? 1905
• What was involved in the Rutherford's experiment? Bombarding thin gold foil with alpha particles.
• What happened during the Rutherford's experiment? Most of the alpha particles went through but not all. Some of the alpha particles were deflected.
• Why were some alpha particles deflected? [2] - Got repelled by the same charge that the alpha particles carried - Repelling charge was heavier than the alpha particle
• What was the conclusion in the Rutherford experiment? [2] - The mass of the atom was concentrated in a central nucleus, which was positively charged - The electrons surround this nucleus
• How did Niels Bohr adapt the nucleur model? By suggesting that the electrons orbit the nucleus at specific distances.
• What did later experiments lead to the idea about the positive charge of the nucleus? "That it can be divided into a whole number of smaller particles each with the same amount of positive charge. These particles were given the name ""proton""."
• What experiments did James Chadwick carry out in 1932? It provided evidence that within the nucleus there was another particle, which was called the 'neutron', leading to further refinement of the nucleur model for the structure of the atom.
• When was the neutron discovered? 1932
• What do unstable atomic nuclei do in order to become more stable? Give out radiation.
• Why is radiation emitted from an unstable atomic nuclei to become stable nuclei? [2] - Depends on why the nucelus is unstable - Random process
• How do you measure the activity of a radioactive source at the rate at which it decays? Becquerels (Bq)
• What is one becquerel equivalent to? It is equivalent to one decay per second. 1Bq = 1 decay per second
• What is the count-rate? The number of decays recorded each second by a detector
• What are the three main types of nuclear raidation? [3] - Alpha (a) - Beta (B) - Gamma (Y)
• What absorbs Alpha particles? Is absorbed by a few centimetres of air or a thin sheet of paper.
• What absorbs Beta particles? Beta passes through air and paper but is abosrbed by a few millimetres of auliminium.
• What absorbs Gamma particles? Gamma is very penetrating and needs many centimetres of lead or many metres of concrete to absorb most of it.
• What does each type of radiation consist of? [2] - Different particles - Electromagnetic radiation
• What is ionising? Capable of knocking electrons from atoms.
• Which type of radiation is the most ionising? Alpha
• Which type of radiation is the least ionising? Gamma
• What are the components of alpha particles? [2] - Two neutrons and two protons (same as a helium nucleus) - Ejected from the nucleus
• What are the hazards of alpha particles? [2] - Highly likely to be absorbed - And cause damage if passing through living cells
• What are the components of Beta particles? [2] - A high-speed electron - Ejected from the nucleus as a neutron turns into a proton
• What are the hazards of Beta particles? [2] - Likely to cause damage if absorbed by living cells - Can penetrate the body to inner organs
• What are the components of Gamma particles? [2] - Electromagnetic radiation - Emitted from the nucleus
• What are the hazards of Gamma particles? - Likely to pass through living cells without being absorbed and causing ionisation