Which of the gases: H2, O2, Cl2, F2, N2 A) heavier than air b) lighter than air?

Air has a molar mass of 29 g / mol.
The atomic mass of elements can be found in the periodic table of D.I. Mendeleev, to find out the mass of gases, you need to multiply the atomic mass by the number of atoms, that is, by the index.
H2, hydrogen has a mass of 2 g / mol; O2, oxygen has a mass of 32 g / mol; Cl2, chlorine has a mass of 71 g / mol; F2, fluorine has a mass of 38 g / mol.
a) O2, Cl2, F2, N2;
b) H2.