Answer: Option (b) is the correct answer.
Explanation:
A covalent bond is defined as the bond which occurs due to sharing of electrons between the combining atoms.
Generally, a covalent bond is formed between non-metals.
For example, both nitrogen and oxygen atoms are non-metals and they combine covalently to form  compound.
 compound.
As nitrogen has 5 valence electrons and an oxygen atom has 6 valence electrons. So, there occurs unequal sharing of electrons between the two. 
Thus, we can conclude that when a covalent bond forms then electrons in valence shells are shared between atoms.
 
        
             
        
        
        
Explanation:
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Answer:
the name for NO is nitrogen monoxide 
 
        
             
        
        
        
Most transition metal form more than one cation but aluminum forms the Al3+ cation only.
 
        
                    
             
        
        
        
In a balloon there is a low pressure within the balloon. This means that the particles are more spaced out. Wheras in the cylinder they are under high pressure, meaning that the particles are much closer together!