Explain why the 4s sublevel fills before the 3d begins to fill as electrons are added.

The energy of the 4-s subshell is lower than the energy of 3-d subshell.

Explanation:

During the filling of electrons in subshells, the lower energy levels are filled before the higher energy levels. Also known as Aufbau principle.

Energy of the sublevel = (n + l)

where : n = Principal quantum number

             l = Azimuthal quantum number(s=0,p=1,d=2,f=3)

Energy of 4-s subshell= (4+0) = 4

Energy of 3-d subshell=(3+2) = 5

Energy of 4-s subshell is lower than the energy of 3-d subshell, that is why 4s orbital is filled before the 3-d subshell.

conduction is the transfer of thermal energy (heat in transfer) due to collisions between the molecules in the object. collisions between adjacent atoms and molecules transfer kinetic energy from the warmer to the cooler object. the objects must be in physical contact.

i think its 5049.

i hope this !