The ability of carbon atoms to form covalent bonds with other carbon atoms is the most unique of its bonding properties. CARBON can also accept electrons or share. Two main reasons why its unique. Hope this helps even though its been 5 days for you.
Answer: The net ionic equation for the cobalt-silver voltaic cell is 
Explanation: In cobalt-silver voltaic cell, one half of the cell consists of cobalt electrode immersed in
solution ( which means that
are present in the solution) and other half of the cell consists of the Ag electrode immersed in
solution ( which means that
is present in the solution)
The two electrodes are joined by the copper wire. The cobalt electrode acts as an anode and the silver electrode acts a cathode.
At anode, oxidation reaction takes place and at cathode, reduction reaction takes place.
At Anode : 
At Cathode: ![[Ag^+(aq.)+e^-\rightarrow Ag(s)]\times 3](https://tex.z-dn.net/?f=%5BAg%5E%2B%28aq.%29%2Be%5E-%5Crightarrow%20Ag%28s%29%5D%5Ctimes%203)
Net ionic equation: 
The answer I believe would be D) All of these
18.The octet rule tells us that in every chemical
reactions, elements will either gain or lose electrons to attain the noble gas electron
configuration. This stable<span> electron configuration is known as the octet configuration
since it is composed of 8 valence. Oxygen’s electron configuration is 1s2 2s2
2p4. So when</span> oxygen reacts with
other elements to form compounds, it completes the octet configuration by
taking 2 electrons from the element
it reacts with
19. Actually pure metals are made up not of
metal atoms but rather of closely packed cations (positively charge particles).
These cations are then surrounded by a pack of mobile valence electrons which
drift from one part of the metal<span> to
another. This is called metallic bond.</span>
20. This is the
energy which is needed to break a single bond. When the dissociation energy is
large, this means that the compound is more stable. Since carbon to carbon
bonds have high dissociation energy, therefore they are not very reactive.
21. Network solids are type of solids
in which the atoms are covalently bonded to one another, so they are very
stable. It takes higher temperature to melt them because breaking these
covalent bonds required greater energy. Some examples are:
- Diamond
<span>-Silicon Carbide</span>
Altitude is the reason why the temprature is different.