2nd group of the periodic table
International System of unites.
The question is incomplete, the complete question is shown in the image attached.
Answer:
1) No, it has the right number of valence electrons but does not satisfy the octet rule.
2) Yes
3) No, it has the wrong number of valence electrons, the correct number is 16
Explanation:
If we look at the first structure in the image(HCN), it easy to see from inspection that nitrogen has three valence electrons as it is normally supposed to have. However, if we count all the electrons around nitrogen, we will notice that they are six instead of eight. Thus nitrogen has not satisfied the octet rule here.
The structure HBr satisfies the octet rule, hence it is a reasonable Lewis structures for the compound shown.
CO2 has 16 valence electrons but the structure shown contains about 20 valence electrons hence it is not a reasonable Lewis structure for the compound.