LEWIS STRUCTURES AND BONDS BONDING THEORIES Lewis Structures
- LEWIS STRUCTURES AND BONDS - BONDING THEORIES
Lewis Structures and Bonding Use NASB to draw dot diagrams. N – electrons needed to fill valence (8 or 2) A- electrons available in atom S – electrons shared = N – A B – formed bonds (S divided by 2)
In Cl 2, the total number of unshared pairs of electrons is 6. Cl + Cl Cl―Cl or Cl: Cl The diatomic molecule N 2 contains a triple covalent bond. N + N N≡N or N⋮⋮N In the N 2 molecule, there is only one unshared pair of electrons in each nitrogen atom.
The HI molecule contains only one single covalent bond. H • + I H―I or H: I There are 2 double covalent bonds in a molecule of CO 2. C 2 O O═C═O or O: : C: : O Carbon monoxide has a triple covalent bond. C O C≡O OR C⋮⋮O
Bonding Theories According to VSEPR theory, molecules adjust their shapes to keep pairs of valence electrons as far apart as possible. VSEPR – Valence Shell Electron Pair Repulsion A stereoactive set is a shared pair or an unshared pair of electrons around the central atom.
The shape of a molecule of CO 2 is linear.
The shape of a molecule of HCN is linear.
The shape of a molecule of CH 4 is tetrahedral.
The shape of a molecule of NH 3 is trigonal pyramidal.
The shape of a molecule of H 2 O is bent.
According to VSEPR theory repulsive forces between unshared pairs of electrons causes water molecules to have their shape.
Bond angle = 109. 5 degrees Example: CH 4 Bond angle = 106. 5 degrees Example: NH 3
Bond angle = 104. 5 degrees Example: H 2 O Bond angle = 120 degrees Example: CO 32 -
Bond angle = 118. 6 degrees Example: O 3 Bond angle = 180 degrees Example: CO 2
Intermolecular Forces Intermolecular forces – forces between 2 molecules Van der Waals forces - weakest attractions between molecules Dipole interactions – polar molecules attracted to one another Dispersion forces – caused by the motion of electrons
Hydrogen bonds – strongest intermolecular forces Hydrogen covalently bonded to a very electronegative atom is also bonded to an unshared electron pair of another electronegative atom. H 2 O is a polar molecule. 2 H • + O H: O: H
- Slides: 16