What is the half-life of a 3 g sample of radioisotope that decayed to 0.75 g in 30 days?

At room temperature what happens to the average kinetic energy of the molecules of a solid, liquid, and a gas

Which type of orbits are found in the principal energy level n = 2 a - s b - s, f c - s, d d - s, p e - s, p, d

The bond energy for the van der waals bond between two helium atoms is 7.9×10−4ev. assuming that the average kinetic energy of a helium atom is (3/2)kbt, at what temperature is the average kinetic energy equal to the bond energy between two helium atoms