click below
click below
Normal Size Small Size show me how
chem exam 3
chem 101
Term | Definition |
---|---|
Steps for Writing Lewis Structures | Find the total valence electrons Put the least electroneg atom in the center. Put two electrons between atoms to form a chemical bond. make octs If central atom does not have an octet, move electrons from outer atoms to form double or triple bonds. |
advanced steps | If you have extra electrons after the above steps add them to the central atom. Note: elements in the Period Three (usually S, P, or Xe) can have more than eight valence electrons. use formal charges |
Notable Exceptions to the Octet Rule | H only needs 2 valence electrons. Be and B don’t need 8 valence electrons. S and P sometimes have more than 8 val. Electrons. Elements in Period Three, Four, etc (on the periodic table) can hold more than 8 valence electrons. |
formal charge equation | formal charge=valence electrons-nobonding valence-(bonding electrons/2) use for S an P |
AX2 | linear 180 deg Sp hybrid |
AX3 | TRIGONAL PLANAR 120 DEG HYBRID SP^2 |
AX4 | TETRAHEDRAL 109.5 DEG SP^3 |
AX5 | TRIANGULAR BIPYRRIMIDAL 120,90, 180 DEG SP^3D^2 |
AX^6 | OCTAHEDRAL 90 SP^3D^2 |
AX2N1 | BENT 120 SP^2 |
AX2N2 | BENT 109.5 SP^3 |
AX3N1 | TRIGONAL PYRAMIDAL 109.5 SP^3 |
AX4N1 | seesaw 90, 120 and 180 |
AX3N2 | T-shaped 90 and 180 |
AX5N1 | square pyramidal 90 and 180 |
AX4N2 | square planar 90 and 180 |
Electron-pair Geometry (LINEAR) | WHEN ANGLE IS 180 |
Electron-pair Geometry (trigonal planar) | 120 DEG |
Electron-pair Geometry (tetrahedral) | 109.5 DEG |
Electron-pair Geometry (trigonal bipyramidal ) | SEASAW AND T SHAPED MOLECULES |
Electron-pair Geometry (octahedral) | `SQUARES |