Copyright © Cengage Learning. All rights reserved Review Atomic Number (Z) – number of protons Mass Number (A) – sum of protons and neutrons Copyright © Cengage Learning. All rights reserved

Some nuclei are unstable; they emit particles spontaneously Some nuclei are unstable; they emit particles spontaneously. This phenomenon is radioactivity. All isotopes of the elements with atomic numbers higher than 83 are radioactive. Mass Number X A Z Element Symbol Atomic Number 1p 1 1H or proton 1n neutron 0e -1 0b or electron 0e +1 0b or positron 4He 2 4a or a particle A 1 1 4 Z 1 -1 +1 2

Nuclear Fission is the process in which a heavy nucleus (mass number >200) divides to form smaller nuclei of intermediate mass and one or more neutrons. Nuclear Fusion is the combining of small nuclei into large ones

Nuclear Fission Nuclear chain reaction Atomic bomb The TNT was set off first. The explosion forces the section of fissionable material together to form an amount considerably larger than the critical mass.

Combining of small nuclei into large ones Nuclear Fusion Combining of small nuclei into large ones Fusion Reaction Energy Released 2H + 2H 3H + 1H 1 6.3 x 10-13 J 2H + 3H 4He + 1n 1 2 2.8 x 10-12 J 6Li + 2H 2 4He 3 1 2 3.6 x 10-12 J