Atoms and Molecules Atoms: The smallest units of each chemical element. Positively charged protons and neutral neutrons in the nucleus. Negatively charged electrons around the nucleus. A single grain of sand can contain 10 million billion atoms. 92 different atoms in nature, from hydrogen (H, 1 proton) and helium (He, 2 protons) up to uranium (U, 92 protons). Molecules: Made of several atoms bound together by electric forces. Internal Energy for Atoms/Molecules Mass: Changes in nuclear reactions, and different atoms (nuclei) can be produced. Electric potential energy: Depends on how far the electrons are from the nucleus. Kinetic energy: In the motion, rotations, and vibrations of atoms and molecules. Gravitational potential energy: Plays a large role over astronomical distances. Big surprise, Quantum Physics: Each kind of atom or molecule can only be in certain specific states! When electrons change state, light can be emitted (electron loses energy) or absorbed (electron gains energy). Carbon Monoxide C O

Plasma is a partially ionized gas. Electrons are ripped from their atoms. Some electrons are free rather than being bound to an atom or molecule. Positive and negative charges move somewhat independently. Plasma is electrically conductive so that it responds strongly to electromagnetic fields. Plasma has properties quite unlike those of solids, liquids or gases and is considered to be a distinct state of matter. Plasmas are the most common phase of matter in the universe, by mass and volume. All stars are made of plasma. Colors are from electrons relaxing to lower energy states when they recombine with ions. Light color is characteristic of the atoms or molecules in the gas. UNR is Plasma Physics Central!!

Plasma Physics and the Earth As the speeding solar wind hits the Earth's magnetic field, it creates a shock wave, compresses the forward side of the field, and stretches the far side into a long magnetotail. The field traps particles into the donut-shaped Van Allen radiation belts, which then protect the Earth against the wind. The interaction of the wind and the Earth's field generate two rings of electrical current that flow around the magnetic poles (which are offset relative to the rotation axis) and that in turn create the aurora borealis. (From Stars, J. B. Kaler, Scientific American Library, Freeman, NY, 1992.) Photo of aurora borealis

Ranges of Plasma

Plasma Propulsion for Deep Space Exploration Ion thruster uses plasma in some part of the thrust generation process. Much less powerful than conventional rocket engines. Very efficient, good for long-distance Interplanetary space travel missions. First developed by Russia during to propel spacecraft to Mars. Now in common use! Plasma Propulsion Engine