Number of Non-Bonding Electrons

Step 3 Subtract the number of shared electrons from the number of valence electrons to get the number of non-bonding electrons. Add these electrons as lone pairs to the atoms surrounding the central atom so that you achieve a noble gas electron configuration for each atom. 

Nonbonded electrons are / v / usually not shown in condensed structures. Atoms in organic molecules (except hydrogen) generally obey the octet rule, so any atom with fewer than four bonds must have a number of non-bonded electron pairs equal to four minus the number of bonds. For example, the oxygen in an alcohol has 4 — 2 = 2 nonbonded electron pairs. 

Eighteen-electron rule — An electron-counting rule to which an overwhelming majority of stable diamagnetic transition metal complexes adhere. The number of non-bonded electrons at the metal plus the number of electrons in the metal-ligand bonds should be 18. The 18-electron rule in transition metal chemistry is a full analogue of the Lewis octet rule . 

This expression can be written alternatively as follows, involving the number of non-bonding electrons if present,... 

There is no facile explanation for the success of the EAN formalism (25) nor for the apparently self-consistent geometric behavior of the various coordination complexes described above. The relationship between total electron count, number of bonded ligands, number of non-bonding electrons and molecular geometry is complex and has been discussed at length (26-29). To tease a full understanding out of all the data, self-consistent as well as contradictory, is to hope for too much. 

The four main characteristics of the transition-metal in a complex that allow to define this complex well are the Nnmber of Valence Electrons (NVE), the Number of Non-Bonding Electrons (NNBE), the Oxidation State (OS) and the Coordination number (C). 

Draw developed (three-dimensional) formula of the following complexes, give their MLnXp form, and determine their numbers of valence electrons (NVE), numbers of non-bonding electrons (NNBE), oxidation states (OS) and their coordination numbers (C) ... 

No. dots = Number of non-bonded electrons on an atom in the structure... 

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