An atom that has an outer shell that is not full is (more likely or less likely) to be reactive than an atom that has a full outer shell.

A half filled orbital is LESS LIKELY to be reactive than a fully filled orbital

Explanation: A fully filled orbital has the electronic configuration of a noble gas. That is, unreactive.

The quantum states of these orbitals(fully filled) are stable because the electrons in the sub shell are fully filled which makes it difficult for it to loose and gain electron unlike a half filled which is much more easier. It will take more energy for ionization to take place making it(fully filled) more stable.

relative dating involves things like higher layers are most recent than rocks lower in the sequence. this can be extended to the known sequence of fossils. rocks containing rabbit fossils are later than those containing dinosaur fossils.  

absolute dating methods mainly use radioactive elements that have known rates of decay and produce recognizable products. for example potassium 40 decays to produce argon. once a rock has solidified the argon is trapped. by measuring the argon and potassium0 you can get an accurate number for the age.  

some other methods are good for archaeological ages. dendrochronology involves recognizing the sequence of tree rings. the orientation of magnetized particles in baked clay can be used to date a fire.

hope this .. .

thats not even an aswer choice