Step-by-step explanation:
- For 1:  
  
The given compound is formed from the combination of hydrogen and nitrogen. It is a colorless gas having a pungent smell.
Hence, the correct answer is ammonia.
- For 2: 
  
The given functional group is known as amine. Two places of nitrogen are occupied by hydrogen and one by alkyl group, thus is considered as a primary amine.
Hence, the correct answer is primary amine.
- For 3: 
  
The given functional group is known as amine. Two places of nitrogen are occupied by alkyl group one by hydrogen, thus is considered as a secondary amine.
Hence, the correct answer is secondary amine.
- For 4: 
  
The given functional group is known as amine. All the three places are occupied by alkyl group, thus is considered as a tertiary amine.
Hence, the correct answer is tertiary amine.
- For 5: 
  
The given group is known as alkyl group such as methyl 
 , ethyl
, ethyl 
 etc..
 etc..
Hence, the correct answer is alkyl group.
- For 6: 
  
All the four places of nitrogen is occupied by hydrogen and it is known as ammonium ion.
Hence, the correct answer is ammonium ion.