Topic:
Structure Lecture of Matter
Positively charged nucleus (10^-15m)
Surrounded by electron cloud (10^-10m)
Atom 100,000 times larger than nucleus
1 AU = 215 Solar Radii (Radius of the sun)
Whereas atom is 10^5 bigger than it's nucleus
Atomic Terminology
Atomic Number
o Number of protons in nucleus
o Determines chemical element name
Atomic Mass Number
o Number of protons + neutrons
Molecules
o Consist of two or more atoms
Isotope
o Same # of protons but different #''s of protons
Phases of Matter
Solid
Liquid
Gas
Phases of same material behave differently because of differences in the chemical bonds
Phase Changes:
Ionization
o Stripping of electrons, changing of atoms into plasma
Dissociation
o Break of molecules into atoms
Evaporation
o Breaking of flexible chemical bonds
Melting
o Breaking rigid chemical bonds
o Changing solid to liquid
*Phase depends on both temperature and pressure*
Electrons are restricted to specific energy levels
Gain release energy in accordance with changes in orbital shells
Astrophysical objects
Combination of 3 types of spectra
o Emission Line Spectrum
Only specific lines visible
o Continuous Spectrum
Visible wavelengths
o Absorption spectrum
Dark absorption lines in continuous spectrum
Thermal Radiation
Emitted by stars and planets and people
Thermal radiation spectrum depends on Properties temperature
of thermal radiation
1. Hotter objects emit more light at all frequencies per unit area
2. Hotter objects emit photon with a higher average energy
Stars have thermal continuum spectra, with absorption features superposed
Chemical Fingerprints: (lines on spectrum)
Each atom has unique energy levels
Each transition corresponds to a unique photon energy, frequency, and wavelength
Downward transitions produce unique pattern of emission lines
Upward transitions produce unique pattern of absorption lines at same wavelengths
Observing fingerprints in a spectrum indicates what atoms are present
Molecules have additional energy levels because they can vibrate and rotate
Large numbers of vibrational and rotational energy levels can make the spectra of these
molecules complicated (inc.)
The Doppler Effect:
Doppler effect measures from shifts in wavelengths of spectral lines
Redshift
o Moving away
Blueshift
o Moving towards
No Doppler shift where an object is orbiting at equal distances
Doppler effect allows us to measure radial velocity of an object
Different Doppler shifts from different sides of rotating object spread out its spectral lines
Spectral lines are wider when an object rotates faster
Higher frequency / wavelength when moving towards you (works with sound as well,
remember the sound example)