Which atom is the smallest atom of all?

Q. A helium atom, a hydrogen atom and a neutron have masses of $4.003u$, $1.008u$ and $1.009u$ (unified atomic mass units), respectively. Assuming that hydrogen atoms and neutrons can fuse to form helium, what is the binding energy of a helium nucleus?

Q. Helium atom is 2 times heavier than hydrogen molecule. At ${15}^{0}C$the average kinetic energy of helium atom is:

Q.

What is the atomicity ? Write the atomicity of hydrogen , helium , chlorine , oxygen , nitrogen

Q. Give the increasing order of the atomic masses of the following elements
(a) Hydrogen
(b) Oxygen
(c) Helium
(d) Carbon

Q. Helium atoms is two times heavier than a hydrogen molecule At $298K$, the average kinetic energy of a helium atom is: