I think it is called a loess. Please correct me if I am wrong.
Answer:
Ne
Explanation:
Atomic number of Ne is 10.
Electronic configuration of Ne:

Octet of Ne is complete . Element having complete octet are stable and behave ideal gas.
and
are reactive and hence, does not behave as ideal gas.
1) D. An element
2) D. Suspension
3) A. Iodine
4) A. Atoms of the same element