PHYS 183 Lecture Notes - Lecture 11: Electromagnetic Spectrum, Mass Number, Atomic Number

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2 Feb 2013
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Lecture 11: January 30th, 2013
electromagnetic spectrum is all of the light in the universe we can only see the visible
spectrum
gamma rays have high frequency; radio waves have low frequency
blue light is higher energy, shorter wavelength than red light
o blue is closer to gamma rays, red is closer to radio waves
nucleus contains positively charged protons and neutral neutrons; cloud of electrons surround
the nucleus
most of the mass in the atoms is in the nucleus
atomic number = # of protons
atomic mass number = # of protons + # of neutrons
ie/ atomic number of H = 1, atomic mass number = 1; atomic number of He = 2, atomic mass
number = 4 (since 2 protons & 2 neutrons)
elements can come in different isotopes different number of neutrons
o C-12 has 6 protons + 6 neutrons; C-13 has 6 protons + 7 neutrons; C-14 has 6 protons +
8 neutrons
a molecule is made up of 2 or more atoms which are bound together chemically share
electrons
o ie/ H2O = 2 H + 1 O
3 phases of matter
o gas water vapour
o liquid water
o solid ice
each phase has different chemical bonds but are made of the same thing
matter changes phase with changing temperature & pressure
important changes:
o melting: breaking rigid chemical bonds between molecules
o evaporation: breaking flexible chemical bonds between molecules
o molecular dissociation: breaking of molecular bonds (turning molecules into atoms)
o ionization: stripping atoms of their electrons
as you increase temperature, matter goes through the following stages:
o solid liquid gas molecular dissociation plasma fully ionized plasma
it takes energy to rip apart atoms
how is energy stored in atoms?
o electrons have potential energy
o electrons stay in energy levels around the nucleus
level one is ground state go up to excited states
energy levels get closer and closer together as you go up
can move from level 1 to level 2 or level 2 to level 1, but you cannot go up or
down half of a level
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