Conjugation and resonance

I'm new to Organic chemistry, and I'm just starting to learn about resonance. I learnt that resonance and conjugation are related - if a system is conjugated, with alternating sigma and pi bonds/pi-sigma-lone pair/pi-sigma-free radical/pi-sigma-p orbital/lone pair-sigma-positive charge arrangements in the same plane, we can derive resonance structures by alternating the bonds/radical/charge between atoms. My question is - can resonance occur without conjugation, and if so, what are the rules governing it?




A good example would be a polar covalent bond; such a bond exists as a resonance hybrid of totally covalent and totally ionic canonicals; switching on and off the (line in a Lewis stucture) respectively.


For example, the carbon tetrafluoride molecule\* is covalent but has significant contributions from an ionic structure involving "a carbon(IV) cation electrostatistically bound to four fluoride anions" in tetrahedral symmetry- a "no lines, just ionic bonds" canonical.


\*which is non-polar but still has polar covalent bonds in it


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