B) ethane has the formula c2h6. in terms of electronic structure,
explain why there is a single covalent bond between the two carbon atoms.

There is one single covalent bond between two carbon atoms.

Explanation:

We know that sharing of electrons form covalent bonds.

If we look upon K,L,M ,N shells of the carbon and hydrogen atoms.

We found that Hydrogen is having only   electron in K shell.

And Carbon on the other hand is having electrons in K shell and electrons in L shell.

So carbon have   valence electrons,and it can share bonds with any relevant atom to complete its octet.

And Hydrogen requires   electron to complete its doublet.

Alkane general formula

For ethane

Carbon atom is shared by   Hydrogen.

The remaining one electron of carbon will be shared with another carbon atom.

An image of the sharing of electrons attached below,

Hence we have only   covalent bond between the two.

c (diamond),

sio2 (quartz)