Name  Lewis Structure Kernel electrons  Valence electrons
Sodium  Na.   1s2 2s2 2p6  3s1
 Phosphorus  phosphorus Lewis dot structure  1s2 2s2 2p6  3s2 3p3
 Bromine  bromine Lewis dot structure

 1s2 2s2 2p6 3s2 3p6 3d10

(≠ [Ar] = 1s2 2s2 2p6 3s2 3p6 )

4s24p5 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ball & stick crystal structure for NaCl

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Clark's Method for determining bonding in covalent Lewis Structures

A Quantum Picture of Atomic Orbitals & Bonding

For a more in-depth understanding of bonding as illustrated with QuickTime movies based on quantum calculations check out the Bonding supplement.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

VSEPR (Valence Shell Electron Pair Repulsion) Theory is based on three assumptions (there are more advanced versions, but unnecessary for us):

VSEPR predicts geometry based on these assumptions in a few simple, sequential, steps:

  1. Draw a correct Lewis Structure.

  2. Determine the Steric Number = the number of bonded atoms + the number of lone pairs = "electron clouds" in valance shell of central atom.

  3. Maximize the angles between electron pairs, placing the lone (unbonded) pairs at the extremes.

 

 

Trigonal planar with angles of 120°


image of trigonal planar structure

 

 

 

 

Tetrahedral with angles of 109.5°


drawing of tetrahedron

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CO2 linear molecular geometry

ball and stick model of carbon dioxide

 

 

 

 

 

 

 

 

 

 

 

Trigonal planar molecular geometry (formaldehyde, CH2O)

ball and stick model of formaldehyde

ball and stick model of formaldehyde

 

 

 

 

 

 

 

 

 

 

 

Tetrahedral molecular geometry (methane, CH4)

ball and stick model of methane viewd in plane of HCH

ball and stick model of methane - offangle view

 

 

 

 

 

 

 

 

 

 

 

 

Trigonal pyramidal molecular geometry (ammonia, NH3) [model]

ball and stick model of ammonia - side view

rotated to view molecule from below

ball and stick model of ammonia - view from below

 

 

 

 

 

 

 

 

 

 

 

Bent molecular geometry (water, H2O)

ball and stick model of water

 

 

© R A Paselk

Last modified 7 October 2008