Nuclear Reactions FissionFusion There is a STRONG NUCLEAR FORCE that holds the neutron and protons together in the Nucleus.

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

CHEMICALNUCLEAR Occurs when bonds are broken or formed. Occurs when nuclei emit particles and/or rays. Atoms remained unchanged, though may be rearranged. Atoms often converted into atoms of another element. Involves valence electronsMay involve protons, neutrons or electrons Small energy changesHUGE energy changes Reaction rates affected by temp and pressure Reaction rate NOT normally affected temp and pressure

Fission Neutrons bombard nucleus splitting nucleus (from heavy to lighter) release 2 things: neutrons and energy

Nuclear Power Plants Fission is controlled by: –releasing neutrons to start the chain reaction –capturing neutrons to slow or stop the reaction.

ISOTOPES

Radioactivity Any process where the nucleus emits particles or energy

Nuclear Decay ALPHA - a particle that has 2 protons and 2 neutrons (helium) is released from an unstable nucleus. Ex: uranium – 238 Fission BETA - occurs when a neutron in the nucleus of a radioactive isotope splits into a proton and an electron. Ex: Carbon - 14 GAMMA - involves the release of HIGH energy and radiation from the nucleus of the atom. Protons, neutrons and electrons not affected. Ex: nuclear power fuels

Chapter 19 Radioactivity and Nuclear Energy

14 : The decay series.

15 A representation of a Geiger- Müller counter.

16 Unstable nucleus.

17 Representation of a fission process.

18 Diagram of a nuclear power plant.

Copyright © by McDougal Littell. All rights reserved. 19 Schematic of the reactor core.

20 Radioactive particles and rays vary greatly in penetrating power.

21 Diagram for the tentative plan for deep underground isolation of nuclear waste.

An alpha particle is a Helium 4 nucleus (two protons and two neutrons). It is produced by nuclear fission in which a massive nucleus breaks apart into two less-massive nuclei (one of them the alpha particle). This is a strong interaction process.

A beta particle is an electron. It emerges from a weak decay process in which one of the neutrons inside an atom decays to produce a proton, the beta electron and an anti-electron-type neutrino.

A gamma particle is a photon. It is produced as a step in a radioactive decay chain when a massive nucleus produced by fission relaxes from the excited state in which it first formed towards its lowest energy or ground-state configuration.

How Far Away? Inverse Square Law

Half-Life Amount of time it takes for ½ the radioactive material to decay

E=mc 2 E  energy m  mass c  speed of light –(3.0 x 10 8 m/s) Small mass=large output Mass of proton and neutron in the nucleus is less than the same protons and neutrons separate?

Critical Mass Minimum fissionable isotopes needed to provide neutrons to sustain chain reaction

Smoke Detectors Alpha emitters –Charged current with smoke Am-241

Nuclear Medicine Used by >>1 in 3 admitted to hospital Biochemical & Physical changes occur in disease before anatomical can be identified

Radioactive Tracers Technetium-99 –6 hr half-life –Accumulate in cells with rapid growth (tumors)

Gadolinium-153 Accumulated in bone –Osteoporosis

Fusion Interior of sun –15 million °C Nuclei combine –H ‘s combine to form He