Combined Science (1-9): Radioactivity Beta Decay and Nuclear Equations

Objectives:

Beta Decay and Nuclear Equations Draw a line under last lesson’s work and write today’s title in your book... 28/11/2018 c/w Beta Decay and Nuclear Equations

FLASHBACK FLASHBACK: Explain the energy transfers that take place during the hydroelectric (dams) production of electrical energy [6 marks]

FLASHBACK- AFL FLASHBACK: Explain the energy transfers that take place during the hydroelectric (dams) production of electrical energy [6 marks] Water is up high so has high gravitational potential energy (GPE) This is transformed into kinetic energy Used to move the turbines The kinetic energy of the turbines is transferred into kinetic energy of a coil The spinning coil/generator then transforms the energy into electrical energy

Starter Activity +2 electron positron Very weak Fill in the table with what you know. The blue row is completely new but you can probably predict it! Nature Mass Charge Ionising ability Alpha (α) +2 Beta (β-) electron Beta (β+) positron Gamma (γ) Very weak

Explore 4 +2 strong 1/1840 -1 weak +1 1/1840 weak Ionising = capable of turning atoms into ions (by removing or adding electrons) Nature Mass Charge Ionising ability Alpha (α) Beta (β-) electron Beta (β+) positron Gamma (γ) 2 protons + 2 neutrons (helium nucleus) 4 +2 strong 1/1840 -1 weak +1 1/1840 weak Electromagnetic wave Very weak

Nuclear Decay Remember, when an atom is unstable (radioactive), it releases this energy in the form of radiation. This process is random and cannot be predicted. This is called decay and changes the structure of the atom

First identify the number of protons and neutrons in a uranium atom Nuclear Decay Write a hypothesis of what you think will happen to the atomic structure of a uranium atom during decay U 92 236

Types of Nuclear Decay Alpha Decay Beta (-) Decay Beta (+) Decay You will need to be able to identify the type of nuclear decay taking place by looking at what has happened to the mass and proton number of a radioactive element. This will build up to understanding nuclear equations Alpha Decay Beta (-) Decay Beta (+) Decay Gamma Decay

Alpha Decay In alpha decay, the unstable nucleus loses 2 protons and 2 neutrons (a helium nucleus) What effect would this have on the mass number and the atomic number? Predict the products of alpha decay of uranium-235 This is a nuclear equation! Pretty simple really!

Beta (-) Decay In beta minus (β-) decay, a neutron changes into a proton within the nucleus. The mass stays the same, but there is now extra positive charge. (extra proton) so an electron is created to cancel out this charge. Firstly, establish what effect this has on the mass number and on the atomic (proton) number ? e- + Now using what you know about elements, use the periodic table to predict the result!

Beta (-) Decay In beta minus (β-) decay, a neutron changes into a proton within the nucleus. The mass stays the same, but there is now extra positive charge. (extra proton) so an electron is created to cancel out this charge. Np e- 235 + 93

Beta (β +) Decay In beta positive (β+) decay, a proton changes into a neutron within the nucleus. The mass stays the same, but there is now less positive charge. (extra proton) so a positron (like a positive electron!) is created to cancel out this charge. Firstly, establish what effect this has on the mass number and on the atomic (proton) number ? β+ + Now using what you know about elements, use the periodic table to predict the result!

Beta (β +) Decay In beta positive (β+) decay, a proton changes into a neutron within the nucleus. The mass stays the same, but there is now less positive charge. (extra proton) so a positron (like a positive electron!) is created to cancel out this charge. Pa β+ 235 + 91

Support: Quick Trick! No Point Being Negative Neutron  Proton is B Negative People Need to Be Positive Proton  Neutron is B positive

Gamma Decay Gamma decay is the simplest! As it is only pure energy, it has no effect on the atomic structure (so no equation to learn!) Discussion point: Where has this energy come from if there is no effect on atomic structure?

Individual Practice

6 mark question! Compare the nuclear rearrangements that occur in beta positive and beta minus decay [ 6 marks]

In beta minus decay, a neutron changes into a proton 6 mark question! Compare the nuclear rearrangements that occur in beta positive and beta minus decay [ 6 marks] In beta positive decay, a proton changes into a neutron This causes the proton number to decrease by 1 but mass to stay the same A positron is emitted In beta minus decay, a neutron changes into a proton This causes the proton number to increase by one but mass stays the same An electron is emitted

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