Answer:
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.
Answer: is the benefit worth the cost?
Explanation: for those on edge :)
You can tell that the atom is in the excited state because:
- Electron configuration should follow the 2-8-8-2 rule, meaning that the inner shell should be filled before the next shell can start holding electrons.
- Instead of the atom's electron configuration being in the ground state at 2-8-8-1, electrons from the second shell have jumped to the third.
H-Cl pair of atoms has the most polar bond.
This is true i think if that is a question
