The energy of electron of opposite spin in the same space orbital is generally .

a
zero
b
about the same
c
infinite
d
extremely different

about the same

Explanation:

From the Pauli Exclusion principle, we know that two electrons occupying a given orbital must exist in opposite spins since no two electrons in an atom has the same value for all four quantum numbers. This principle establishes the maximum occupancy of each orbital as two electrons per orbital.

However, the both electrons in the orbital are in an orbital of a particular energy. The two electrons are in the same energy level and energy sublevel hence their energies are about the same, just that they exhibit different orientations in a magnetic field.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.  

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.