Atomic/Covalent Bonding Theories: Is There One That Is Best?

[Achrelos]

I'd like to start off by saying I'm new here, since this is my first post and I didn't notice an introduction section.

 

In my first semester Gen Chem class we started to discuss covalent bonds, reviewed Lewis dot structures, and learned to draw VSEPR sketches. I immediately noticed that there was an inadequacy in what we have been taught up to now when I began coming across interhalogens and other molecules that boldly broke the octet rule. She (my professor) said we would get into more complex models, but they too would have issues. I read ahead in our text book and have a rudimentary (at best) understanding of valence bond theory and molecular orbital theory. But then since neither of those works for everything they are used in combination sometimes.

 

My question is: Does there exist a singal modal that work s for everything concerning the atom and bonding? If not, which is the best we currently have?

 

Looking forward to being part of this forum.

[studiot]

No, there is no, best theory.

Ideas like most 'delicious ice cream', 'fastest car', 'favourite colour' belong in the junior school playground, not in the study of Science.

In Science we look for theories that correspond to observations and are (or should be) prepared to modify these theories in the light of new observations.

 

Atoms bond together because the resultant structure offers the components a lower energy state, or states, than separate existence. Note carefully this may not be the lowest energy state (compare with what I said about best).

 

Just as an architect has many ways to assemble his building, Nature has many ways to assemble atoms.

 

Bonding occurs by interaction between some the electrons in the components.

 

Usually, but not always, it takes place between some of outermost electrons.

 

The octet rule was postulated before the periodic table was fully worked out. At that time they did not know about transition elements.

 

When studying bonding, it is usual to begin with the assembly of a few atoms to form simple molecules.

Ionic and covalent bonding are introduced.

At some point the idea of delocalisation is introduced. This means that new structures are introduced where the bonding electrons are no longer attributable to individual atoms, they 'belong' to the bonded complex or structure.

This introduces a very important form of bonding, metallic bonding, where enormous numbers of atoms and electrons are involved in combining to form a single structure. It also endows the metallic structure with additional properties, not enjoyed by the majority of ionic or covalent compounds.

Later minor forms of bonding are studied. These include bonds such as Van der Waals bonds that transient and simply modify existing properties.