Atoms

Atoms

1. Protons

   • Positive Charge
   • Part of every nucleus in elements
   • Atomic number = the number of protons in that element
     • Atomic # is always above or below the atomic symbol
   • Attracts Electrons
   • Relative Mass: 1,836

2. Electrons

   • Negative Charge
   • You can't know its precise position or location
     • Uncertainty Principle
   • In the electron cloud
   • Attracts Protons
   • J. J. Thomson - first to discover electrons
   • Relative Mass: 1
   • Electron is "smeared out" into a wave-like "cloud"
   • To "see'' the electron, you have to interact with it

3. Neutrons

   • 0 Charge
   • Neutrons determine isotopes of the element
     • Mass number = # of protons + # of neutrons
   • Part of most of the nuclei of elements
   • Relative Mass: 1,839

4. Nucleus

   • Protons
   • Electrons
   • Neutrons
   • Rutherford discovered the nucleus by doing the helium ion experiment
   • Contains more than 99% of the atom's mass

5. Elementary Charge

   • Denoted as "e"
   • Always comes in units of +e or -e
   • Only possible to have multiples of e, such as +e, -e, +2e, -2e
   • Impossible to have fractions of e such as -0.5e, +0.5e, -1.5e, +1.5e

6. Forces

   • Electromagnetic Forces
     • Electrons are bound to the nucleus by attractive forces between protons and electrons
     • The energy of an electron causes it to move around the nucleus instead of falling in
   • Strong Nuclear Force
     • Strongest known force in science
     • Attracts neutrons and protons and works at extremely small distances
     • For every atom heavier than helium, there is at least 1 neutron for every proton
   • Weak Force
     • 2nd weakest force
     • Breaks down nuclei
   • Gravity
     • Weakest force -- Needs large mass to create an impact

7. Radioactivity

   • Alpha Decay
     • Atom ejects 2 protons and 2 neutrons
     • 2 protons + 2 neutons = Helium-4
     • Atomic # is decreased by 2; mass # is decreased by 4
   • Beta Decay
     • This is when a neutron splits into a proton and an electron; the electron is ejected
     • Atomic # increases by 1; mass # stays the same
   • Gamma Decay
     • Nucleus emits energy by gamma rays

8. Light

   • Light comes from atoms
   • The colors perceived in a spectroscope is different for each element
   • The process of atoms emitting and absorbing light are the reasons that our clothes, paint, and other things have color
   • Each individual line perceived in a spectroscope is called a spectral line
   • A spectroscope is a device that splits light into different colors based on the element
   • Comes in tiny bundles called photons
   • Amt. of energy in a photon determines the color of light
   • Red light = lower energy; blue light = higher energy
   • Neils Bohr was a Danish physicist who proposed the concept of energy levels
   • Electrons cannot remain in between energy levels
   • Electrons change levels by absorbing or emitting light
   • When an electron moves from a higher level to a lower level, the atoms give up the same amount of energy as they absorbed
   • The colors in spectral lines correspond to the differences in energy between energy levels

9. Quantum Theory

   • Says that when thing get too small, matter and energy do not obey Newton's laws
   • Classical laws are not obeyed in the same way as with a larger object
   • When a particle is confined to a small space, then the energy, momentun, and other variables are restricted

10. Energy Levels

    • The closer to the nucleus the electron is, the lesser energy is in the electron
    • When the nucleus is farther away from the electron, the more energy the electron has
    • The energy levels occur because the electrons are at different average distances from the nucleus
    • The energy of an electron must match 1 of the energy levels in the atom
    • When electrons are added to an atom, they settle into the lowest unfilled energy level
    • Energy levels are predicted by quantum mechanics, a branch of physics that deals with the microscopic world of atoms
    • 1st level = 2 electrons; 2nd and 3rdl evels = 8 electrons; 4th and 5th levels = 18 electrons
    • Each element fills the energy levels to a different point