6A

• Chemical bonds

  Atoms exchange electrons to maximize stability, or rearrange electrons
• Octet rule

  When atoms gain a full valence shell of 8 electrons, they gain maximum stability
• The octet rule does not apply to transition and inner transition metals on the first 4-5 elements in the table</b>
• Atoms may lose, take electrons to gain a full valence shell
• Elements tend to exchange the minimum amount of electrons when bonding
• Atoms with less than 4 electrons tend to lose electrons due to their low ionization levels and atoms with more than 4 electrons gain electrons due to their high electron affinities
• Covalent bonds

  Bonds formed by sharing electrons (strong)
• Ionic bonds

  Atoms with higher electron affinity take electrons from other atoms when bonding (strong, weak)
• Metallic bonds

  Atoms with weak electron affinities bond by sharing their easily lost electrons among many atoms, these electrons are mobile and no longer associated with a nucleus
• Polarity

  Tendency of an object to form two localized regions of opposite character
• A bond is polar if electrons are unequally shared between 2 atoms
• Polar bonds are stronger because the attraction of opposite charges of the polarized atoms holds them together</b>
• Electronegativity

  An element's ability to attract electrons
• Covalent bonds have small-medium polarities
• ionic bonds have high polarities
• nonpolar covalent bonds

  EN< 0.5
• polar covalent bond

  EN= 0.5-1.7
• ionic bond

  EN> 2.0