Xenon

1)
Refer to the webpage below. Xe can react with F2 to give different fluorides.
Xe(g) + F2(g) → XeF2(s) + XeF4(s) + XeF6(s)
All valence 5s and 5p electrons of Xe are paired up. These valence electrons can absorb energy to promote themselves to the low-energy empty 5d orbitals. Therefore, there are orbitals with unpaired electrons. Each of such orbitals can overlap with a valence 3p orbital with unpaired electron to form an Xe-F covalent bond. The energy required for promotion of electrons is compensated by the energy released in the formation of strong Xe-F bonds.
However, He cannot react with F2. Actually, He has no reaction at all. This is because He atom does not have low-energy empty d orbitals for promotion of valence 1s electrons.

2)
He has a density much lower than that of air, while Xe has a density much higher than that of air. Therefore, a balloon (or airship) filled with He gas can go up in air, while a balloon (or airship) with Xe gas cannot.

1)due to the larger size of xenon,it have more electrons,although it is noble gas, it can be react to form complex where helium cannot.(helium is samll in size due to only 2 electrons around the nucleus.

2)xenon cannot. helium can ,because it is lighter than air ,however, xenon is too heavy.