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Delivery guides are designed to represent a body of knowledge about teaching a particular topic and contain:
- Content: A clear outline of the content covered by the delivery guide;
- Thinking Conceptually: Expert guidance on the key concepts involved, common difficulties students may have, approaches to teaching that can help students understand these concepts and how this topic links conceptually to other areas of the subject;
- Thinking Contextually: A range of suggested teaching activities using a variety of themes so that different activities can be selected which best suit particular classes, learning styles or teaching approaches.
Assessable content statements:
P4.3a recall that atomic nuclei are composed of both protons and neutrons, that the nucleus of each element has a characteristic positive charge
P4.3b recall that atoms of the same elements can differ in nuclear mass by having different numbers of neutrons
P4.3c use the conventional representation for nuclei to relate the differences between isotopes
P4.3d recall that some nuclei are unstable and may emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma rays
P4.3e relate these emissions to possible changes in the mass or the charge of the nucleus, or both
P4.3f use names and symbols of common nuclei and particles to write balanced equations that represent radioactive decay
P4.3g balance equations representing the emission of alpha, beta or gamma radiations in terms of the masses, and charges of the atoms involved (M1b, M1c, M3c)
P4.3h recall that in each atom its electrons are arranged at different distances from the nucleus, that such arrangements may change with absorption or emission of electromagnetic radiation and that atoms can become ions by loss of outer electrons
P4.3i recall that changes in atoms and nuclei can also generate and absorb radiations over a wide frequency range
P4.3j explain the concept of half-life and how this is related to the random nature of radioactive decay
P4.3k calculate the net decline, expressed as a ratio, during radioactive emission after a given (integral) number of half-lives (M1c, M3d)
P4.3l recall the differences in the penetration properties of alpha-particles, beta-particles and gamma-rays
P4.3m recall the differences between contamination and irradiation effects and compare the hazards associated with these two
An approach to teaching the structure of the atomic nuclei is to make it more visual for learners. Learners could be provided with string and beads of 2 different colours. One colour for protons and one for neutrons. Teachers may display an element from the periodic table on the board and ask the learners in pairs to model it. This can be taken further to model isotopes, which is highlighted by statements P4.3a-c. Radioactive decay (P4.3d-g) could be introduced by pairing learners up and providing each group with a sheet containing several radioactive decay equations. Learners should be able to note down change in atomic mass and number which should help them to explain what has changed in terms of the numbers of protons and neutrons.
Common misconceptions or difficulties learners may have
Learners find it difficult to understand the concept of half-life and giving the net decline using a ratio (P4.3k). To overcome the difficulty learners may be provided with 100 wooden cubes with one side coloured and asked put them into a beaker and shake them out over a table and remove those with the coloured side up. Once removed learners should record the number remaining and use these to repeat the process till no blocks remain. They can use these results to plot a graph of number of cubes remaining against number of throws. This should give them a curve resembling a half-life decay graph. They can use the graph to determine how many throws it takes to halve the number of blocks. This can be related to actual half-life graphs which look at activity and time taken to understand the concept with a little more clarity.
During radioactive decay learners find it difficult to understand that when a beta particle is released a neutron is turned into a proton. Generally they think it is an electron being released as on the radioactive decay equation it is illustrated with a negative sign. Extra care needs to be taken when explaining the equations.
Conceptual links to other areas of the specification – useful ways to approach this topic to set learners up for topics later in the course
The atomic model (P4.3a) is a key concept which is fundamental in the topic 'Matter (P1.1a-c)'. Ensuring clear understanding early is critical.
Introduction to electromagnetic radiation (P4.3d) has occurred in a previous topic 'The electromagnetic spectrum (P4.2a, b and g)'.
Learners are to look into the death of Russian ex-spy Alexander Litvinenko that has been linked to the presence of a ‘major dose’ of radioactive polonium-210 in his body. Learners are to use their knowledge of radioactive materials and research to explain how this may have caused his death. This may be written as a literacy report or a presentation. A good place to start could be the BBC news website.
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