CHEMISTRY

• Atoms are ridiculously and unbelievably small
• A single human hair is about as thick as 500,000 carbon atoms stacked over each other
• A fist contains trillions and trillions of atoms
• If one atom in a fist were about as big as a marble

  The fist would be about the size of Earth
• Imagining the size of atoms

  1. Fingertip as big as a room

  2. Room filled with rice grains (each representing a cell)

  3. One cell as big as the room

  4. Cell filled with rice grains (each representing a protein)

  5. Empty spaces filled with fine sand grains (representing the size of atoms)
• Atom


  Consists of three elementary particles: neutrons, protons and electrons
• Protons and neutrons

  • Bind together and form the atom core, held together by the strong interaction, one of the four fundamental forces in the universe
  • Made from quarks and held together by gluons
• Quarks


  Might literally be points, like in geometry, zero-dimensional
• Electrons


  • Orbit the atom core, travel at a speed of about 2,200 km/s, fast enough to get around the Earth in just over 18 seconds
  • Fundamental particles
• 99.999999999999% of an atom's volume is just empty space
• The empty space is actually filled by quantum fluctuations, fields that have potential energy and build and dissolve spontaneously
• If you subtract all the spaces between the atom cores from the Empire State Building, it would be about as big as a rice corn
• All the atoms of humanity would fit in a teaspoon
• In a neutron star, atom cores are compacted so densely that the mass of three Suns fits into an object only a few kilometers wide
• Electrons


  • Are like a wave function and a particle at the same time
  • We can calculate where an electron might be at any given moment in time
  • These clouds of probability, called orbitals, are where electrons might be with a certainty of 95%
  • The probability of finding an electron approaches 0 the further we get away from the atom core, but it actually never is zero, which means that, in theory, the electron of an atom could be on the other side of the universe
• Just three elementary particles (protons, neutrons, electrons) make up all the matter in the universe
• All atoms of the same element are identical
• Our model of atoms has changed a number of times since we first conceived it, and the current one will certainly not be the last
• Electrons


  Particles found outside of the nucleus
• Protons


  Particles that carry a positive charge
• Neutrons


  Particles that carry a neutral charge
• Opposite charges attract


  Electrons are attracted to the nucleus
• Electron orbit


  Maintained by the combination of electrostatic force and tangential velocity
• Electron capture


  Process where an electron falls into the nucleus, changing the chemical identity of the substance
• Ion


  A particle with unequal numbers of electrons and protons
• Like charges repel


  Protons in the nucleus should repel each other
• Strong nuclear force


  Force that keeps the nucleus together, stronger than electrostatic force
• Proton mass: 1.672 x 10^-27 kg
• Neutron mass: 1.6749 x 10^-27 kg
• Electron mass: 9.11 x 10^-31 kg
• Atomic mass unit


  Approximately equal to the mass of a proton or neutron
• Electron mass is negligible compared to proton and neutron mass
• Particle with greatest mass is the neutron
• Net charge of an ion with 12 protons and 9 electrons is +3
• Statements about atoms and ions

  • Atoms are electrically neutral
  • Ions have unequal numbers of protons and electrons
  • Ions carry a positive or negative charge
  • Ions have equal numbers of protons and neutrons (false)
• Cation


  Positively charged ion
• Anion


  Negatively charged ion
• Matter is anything that has weight and takes up space
• Weight


  How heavy something is
• Volume


  The amount of space that matter takes up