Question 4 unsaved when writing electron configuration the 3d block comes after the 4s block. question 4 options: true false

True

Explanation:

According to Aufbau's principle "sublevels with lower energies are filled up before those with higher energies".

Sublevels do not fill up in numerical order but there is a certain manner in which they are filled. The pattern is shown below:

  1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p e.t.c

 We see that the 4s gets filled before the 3d sublevel.

water is used to store them because it would keep the radiation from getting out in the open and causing harm to the workers