Notes

Outline

Technical Physics 2 Chapter 40 Atomic Structure

Protons, Neutrons & Electrons Protons in nucleus 1 amu +1 charge

Identifying elements Atomic number (Z) the atomic number is equal to the number of protons in the nucleus Mass number (A) the mass number is equal to the number of protons plus neutrons (N) in the nucleus

Isotopes Each isotope has a unique number of protons plus neutrons called the mass number. Mass number = protons + neutrons

Identifying isotopes by symbols

Using the periodic table Atomic number unique to each element equal to the number of protons equal to the number of electrons Atomic weight average weight of all isotopes of that element Isotopes are atoms of the same element with different numbers of neutrons.

Describe the arrangement of information on the periodic table

Organizing the periodic table Metal vs Nonmetal Groups Alkali metals Alkaline earths Halogens Noble gases Periods

What holds it together ? Nuclear forces strong force - overpowers the electrostatics force to hold the particles together in the nucleus weak force - involved in beta decay Binding energy  E = mc2 energy released in building an atom due to the difference in the mass of the atom compared to the mass of the individual particles

Radioactivity The emission of particles or energy (photons) from the nucleus of an atom Alpha particles (a) - a He nucleus, they have relatively little penetrating power Beta particles (b) - beta negative (electrons) and beta positive (same mass as an electron but opposite sign) have greater penetrating power than a Gamma rays ( g) - high energy electromagnetic waves, similar to light but much higher frequency, have the greatest penetrating power.

Nuclear reactions Fusion - “build up” atomic nuclei releasing the binding energy require extreme temperature research in “cold fusion” Fission - “break apart” atomic nuclei releasing neutrons, beta particles and/or gamma rays nuclear reactors nuclear bombs