I think it's 2 I tried looking it up because I was not sure.
#1
- See H and C have shared their electrons so it's Covalent bonding
#2
Yes here we can see the dots and crosses clearly.
#3
It's Methane or CH_4
#4
There is no double bond
Answer: Isotopes of an atom are different because they have different atomic masses and different number of neutrons within their nucleus. They are the same since they will always have the same atomic number/number of protons in their nucleus.
Explanation:
