AP Chemistry Lesson 1.4 Nuclear Chemistry J. Venables Northwestern High School

Metals Metallic character refers to the properties of metals (shiny or lustrous, malleable and ductile, oxides form basic ionic solids, and tend to form cations in aqueous solution). Metallic character increases down a group. Metallic character decreases across a period. Metals have low ionization energies. Metals form positive ions.

Nonmetals Gain electrons to form negative ions. Do not conduct electricity. Metalloids Metalloids have properties that are intermediate between metals and nonmetals. Example: Si has a metallic luster but it is brittle. Metalloids have found application in the semiconductor industry.

Types of Radiation Type of Radiation Symbols Particle Alpha Beta Gamma

Types of Radiation Type of Radiation Symbols Particle Alpha α Helium nucleus Beta β electron Gamma γ High energy electromagnetic radiation

Relative Penetrating Power of Radiation Types

Effect of Electric Field on Radiation + -

Balancing Nuclear Equations The sum of the mass numbers on each side of the equation must be equal. The sum of the atomic numbers on each side of the equation must be equal.

Examples – complete the following nuclear equations

Alpha Decay Examples – Complete the equations for alpha decay:

Beta Decay Examples – Complete the equations for beta decay:

Half-Life The amount of time it takes for one half of a radioactive nucleus to decay. Example – If you start with 1000 kg of 235U, the half-life is the amount of time that passes before you have 500 kg left. 222Rn decays by alpha decay with a half-life of 3.8 days. Write a balanced equation. If you start with 10.0 g of 222Rn, how much will be left after 15.2 days?

Nuclear Fission A large nucleus splits into smaller, more stable nuclei. Started by neutrons striking the unstable nucleus. Chain reaction – neutrons produced. Used to create electricity (fission of ) Can be controlled Used in nuclear weapons (uncontrolled)

Fission A uranium-235 atom absorbs a neutron, and fissions into two new atoms (fission fragments), releasing three new neutrons and some binding energy. One of those neutrons is absorbed by an atom of uranium-238, and does not continue the reaction. Another neutron is simply lost and does not collide with anything, also not continuing the reaction. However one neutron does collide with an atom of uranium-235, which then fissions and releases two neutrons and some binding energy. Both of those neutrons collide with uranium-235 atoms, each of which fission and release between one and three neutrons, and so on. Source: Wikimedia Commons

A Fission Reactor

Nuclear Fusion Two small nuclei are fused (combined) to form a larger, more stable nucleus Requires large amounts of energy to start (only occur at very high temperatures) Produces VERY large amounts of energy. The process by which the sun produces energy.