When an electric circuit is created, electrons begin to move where?

from the negative electrode first

throughout the circuit all at once

from the closed switch first

from the positive electrode first

Electrons are like that in a wire. If one moves they all have to move. Thus when you turn on a switch an electrical potential difference (created by a generator) immediately causes a force that tries to move the electrons.

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.