Dmitri Mendeleev, he realized that the physical and chemical properties of elements were related to their atomic mass and arranged them into groups (columns)
P=0.0902 g/l
v=22.4 l/mol (stp)
M=vp
M=22.4 l/mol * 0.0902 g/l=2.020 g/mol
M=2.020 g/mol
The fewer the carbon atoms, the closer it is to being a gas. The only one you have to check out is A which is hexane. You know that gasoline at the pumps has 8 carbons and its a liquid. So B and C are both not gases because they are above 8.
C6 (hexane) is a liquid at room temperature not a gas.
The answer is D. If there is a gas present, it must be C3
Carbonates
OPTION A is the correct answer
Answer:
One or more number of species which have same number of atomic number but different mass number are called isotopes.
For example, 
are the isotopes of hydrogen.
So here, the atomic number of each of these isotopes is 1 and have different mass number, that is, 1, 2, 3.
