Answer to this is Radioactive isotopes.
Isotopes are the species of the same element having different atomic masses that means the number of protons remains the same but number of neutrons do differ. For example
and
are the two isotopes of Hydrogen (
).
Radioactive isotopes are the isotopes which release some kind of energy in the form of alpha particles, beta particles or gamma radiation. Examples of each of the decay processes are :
Alpha Decay: In this decay one alpha particle having atomic mass 4 and atomic number 2 or we can say a He molecule will come out. 
Beta Decay: In this decay a
particle is emitted increasing the atomic number of the reactant by 1 unit.

Gamma Radiation: In this type of reaction only radiation is emitted out which does not change the original molecule.

A chemical reaction is the process by which a CHANGE takes place (?)
#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:
Yes
Explanation:
Based on the graph, nuclear energy is one of the least contributors of CO2 emissions.
You would support this source of energy .