AP Chemistry · Summary

Unit 2 summary

  1. Bond polarity follows the electronegativity difference; a metal with a nonmetal and a large difference gives an ionic bond.
  2. Lattice energy follows q1q2r\frac{q_1 q_2}{r}: compare charges first, then ion size. Higher charges and smaller ions mean a stronger lattice.
  3. Higher bond order means a shorter, stronger bond. Breaking any bond takes energy.
  4. Count valence electrons with the ion's charge, complete the outer octets, and put leftovers on the central atom; only period 3 and below can exceed eight.
  5. Formal charge = valence − lone-pair electrons − ½(bonding electrons); prefer charges near zero, with negative charge on the more electronegative atom.
  6. Every bond and every lone pair on the central atom is one domain; the domains set the arrangement, and the atoms alone name the shape.
  7. A molecule is polar only when it has polar bonds that its shape does not cancel.