physics

• Matter


  The material that makes up the universe - everything that takes up space and has mass
• Atom


  The simplest forms of matter, consisting of smaller particles called protons, neutrons and electrons
• Atom


  • Protons and neutrons make up the nucleus
  • Electrons move around the nucleus in layers, forming an electron cloud

  
• Fundamental forces in an atom

  • Electromagnetic force
  • Strong force
  • Weak force
• Protons


  Have a positive electrical charge, make up the nucleus with neutrons

  
• Neutrons


  Have no electrical charge, help produce the strong force to bind the nucleus
• Electrons


  Have a negative charge, orbit the nucleus in shells

  
• Atoms are mostly empty space, but electrons prevent atoms from occupying the same space
• Chemical element


  A substance that cannot be broken down into simpler substances by ordinary chemical processes
• There are 118 known chemical elements presented on the Periodic Table

  
• Atomic shells/orbits


  Regions or layers where electrons are found, described by shell numbers or letters

  
• Maximum number of electrons in each shell = 2n^2, where n is the shell number
• Carbon has an atomic number of 6, so it has 6 protons and 6 electrons in a neutral state

  
• Electron shell


  Basic regions or layers where you find electrons

  
• Shell number (n)


  1 being closest to the nucleus, 2 the next closest, up to Q being the farthest away
• Maximum number of electrons in each shell

  2n^2, where n is the shell number
• The third electron shell (n=3) would have 2 x 3^2 = 18 electrons
• Building atomic models


  1. Determine atomic number

  2. Calculate number of electrons in each shell

  3. Ensure outer shell has max 8 electrons
• Atomic number


  Number of protons in the nucleus

  
• Mass number


  Sum of protons and neutrons in the nucleus
• Number of electrons equals number of protons, making the atom electrically neutral
• Electron shells


  • First shell holds 2 electrons, next shell holds up to 8 electrons, subsequent shells can hold more
• Valence shell


  Outermost shell, its electrons play an important role in electrical conductivity and bonding
• An element with a full outer shell (8 electrons) is chemically inert and an electrical insulator
• Periodic table


  Elements are placed in order based on atomic number, position provides information about electron arrangement

  
• Atomic number


  Number of protons in a single atom of the element
• Chemical symbol


  Abbreviation of the element's name
• Relative atomic mass


  Average mass of the atoms of an element, not a whole number due to isotopes
• More than half the mass of a copper atom is made up of neutrons
• Isotopes


  Atoms of the same element with different mass numbers due to different numbers of neutrons

  
• Chemical bond


  Force that holds atoms together in molecules
• Covalent bond


  Sharing of electrons between atoms to fill their valence shells
• Covalent bond


  • Oxygen and hydrogen atoms forming water (H2O)

  
• Ionic bond


  One atom gives up valence electrons to another, forming positive and negative ions that are attracted
• Ionic bond


  • Sodium and chlorine forming sodium chloride (table salt, NaCl)
• Cation


  Positively charged ion formed when an atom loses electrons
• Anion


  Negatively charged ion formed when an atom gains electrons
• The number of protons in an atom is much more stable than the number of electrons
• Molecule


  Bonded combination of atoms
• Compound


  Molecule comprised of multiple different atoms in a fixed ratio