Covalent bond means that the atoms involved will exchange valence electrons gain valence electrons share valence electrons lose valence electrons

Share valence electrons

Explanation:

Covalent bonds are also known as molecular bonds. This is the type of bond that occurs between non-metals and non-metals. This type of bond can happen between two of the same elements or with other elements that are usually positioned near each other in the periodic table.

This is different from ionic bonds where atoms are lost or gained. This type of bonds occur between metals and non-metals.

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.

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a few examples of ethical concerns involving genetically engineering of humans include

-privacy of genetically tested people

- potential side effects

-long term effects