Sorry, but you’re going to have to explain how oxygen can get into a pure silicon crystalline matrix. It might stick to the outermost Silicon atoms (I’m unsure about that), but that would not be a factor in diameter or mass.
A Silicon surface spontaneously oxidzes to SiO2 to a thickness of about 40 Angstroms at room temperature and then stops. This is a bit of a headache for semiconductor manufacturing processes. To get more SiO2 to grow on the Si you need to elevate the temperature and add steam. We used to use about 900 C and burn H2 in the furnace tube for the steam.
Si is fairly unreactive to most chemicals. To etch or dissolve Si with wet chemistry a mixture of HF and HNO3 some times with a little Iodine in the etchant.
The number of atoms of Si would be equal to 6.02x10^23 x (the number of Moles in 1Kg of Si) with a small error for the surface oxide and what ever gases are dissolved in the crystal lattice.
I ALREADY explained that I am NOT talking about the damned balls; but SILICON, the element.
The ELEMENT is reactive; the JOURNALIST makes the error of claiming it ISN'T, because he did not understand, that as you & others say, it won't have any practical effect on the balls.