Lewis Structures, Covalent Bonding, and Electronegativity Firas Cheema

Covalent Bonds Between two nonmetal elements Electrons are shared rather than lost or gained In covalently bonded molecular compounds, intermolecular forces are generally much weaker than the covalent bonds Can be modeled with a Lewis structure

Covalent Bonds Using Lewis Model Lewis structures shows molecular compounds as neighboring atoms sharing some or all of their valence electrons in order to attain octets(duet for H). A shared pair of electrons is called a bonding pair A pair that’s associated with only one atom is called a lone pair Bonding pair of electrons represented by a dash When two pairs shared it’s a double bond, three is a triple bond Lewis model also shows why elements are diatomic Ex. (Chlorine, Nitrogen, etc.)

Practice Problem Write the Lewis structure for: SCl2 CH4

Polar Covalent Bonds Where electrons are unequally shared between elements There is a positive and negative pole The partial positive charge is written with a delta plus above it, the partial negative with a delta negative Is the intermediate between a pure covalent bond a pure ionic bond Most covalent bonds between dissimilar atoms are actually polar covalent

Electronegativity The ability of an atom to attract electrons to itself in a chemical bond Trends: Generally increases across a period Generally decreases down a group Electronegativity is inversely related to atomic radius because the larger the atom, the less ability it has to attract electrons to itself in a chemical bond

Practice Problem Which element is more electronegative? Carbon or Fluorine Sodium or Potassium Francium or Cesium