1 Ch 9 - Nuclear Radiation 1.Nuclear Emissions 2.Nuclear Equations 3.Producing Radioactive Isotopes 4.Half-Life 5.Nuclear Fission and Fusion 6.Uses & Effects

2 Review Remember Protons: + charge Neutrons: neutral Electrons: - charge atomic symbol atomic number number of protons mass number number of protons and neutrons Nuclear Symbols Nuclear Symbols – notice mass number is on top

3 1. Nuclear Emissions Radiation comes from the nucleus of an atom. Unstable nucleus emits a particle or energy  alpha  beta  gamma non-radioactive particle = neutron

4 Alpha Particle Same as a helium nucleus (He) 4 2 He or  Two protons Two neutrons

5 Beta Particle  An electron emitted from the nucleus 0 e or   1 A neutron in the nucleus breaks down 11 0 n H +e

6 Gamma  Radiation Pure radiation Like an X-ray but comes from the nucleus

7 Radiation Protection Shielding alpha – paper, clothing beta – lab coat, gloves gamma- lead, thick concrete Limit time exposed Keep distance from source

8 Radiation Protection

9 2. Nuclear Equations In the reactants and products Atomic numbers must balance and Mass numbers must balance

10 Alpha decay

11 Beta decay 234 Th  234 Pa + 0 e  1 beta particle

12 Gamma radiation No change in atomic or mass number 11 B 11 B + 0  boron atom in a high-energy state

13 Learning Check To predict the product, simply remember that the mass number and atomic number are conserved What is the identity of X?

14 Learning Check Write the nuclear equation for the beta emitter Co-60.

15 Solutions 60 Co 60 Ni + 0 e Np

16 3. Producing Radioactive Isotopes Bombardment of atoms produces radioisotopes = 60 = Co + 1 n 56 Mn + 4 H e = 27= 27 cobalt neutron manganese alpha atom radioisotope particle

17 Learning Check What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He ? + 1 n 5 2 0

18 Solution What radioactive isotope is produced in the following bombardment of boron? 10 B + 4 He 13 N + 1 n nitrogen radioisotope

19 4. Half-Life of a Radioisotope The time for the radiation level to fall (decay) to one-half its initial value

20 Examples of Half-Life Isotope Half life C sec Ra days Ra days I days C years U years

21 Learning Check The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

22 Solution t 1/2 =13 hrs 26 hours = 2 x t 1/2 Amount initial =64mg Amount remaining = 64 mg x ½ x ½ = 16 mg

23 5. Fission VS Fusion Fission large nuclei break up 235 U + 1 n 139 Ba + 94 Kr n Energy

24 Fission of Uranium-235 Chain reaction – the reaction sustains itself by producing more neutrons

25 Nuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n Occurs in the sun and other stars Energy Excessive heat can not be contained Attempts at “cold” fusion have FAILED. “Hot” fusion is difficult to contain

26 Learning Check Indicate if each of the following are (1)Fission(2) fusion A.Nucleus splits B.Large amounts of energy released C.Small nuclei form larger nuclei D.Hydrogen nuclei react Energy

27 Solution Indicate if each of the following are (1)Fission(2) fusion A. 1 Nucleus splits B Large amounts of energy released C. 2 Small nuclei form larger nuclei D. 2 Hydrogen nuclei react

28 6. Uses & Effects Radiation - treatment of cancer Nuclear medicine - use of radioisotopes in diagnosis –Tracers – small amounts of radioactive substances used as probes to study internal organs –Nuclear imaging – medical techniques involving tracers Food Irradiation –Food - irradiated with g rays from 60Co or 137Cs. –Irradiated milk - shelf life of 3 mo. w/o cooling. –USDA - approved irradiation of meats and eggs

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30 Exposure Sources