How many electron shells are in period 1

The electron configuration for chromium is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 5 4 s 1 instead of 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 3 d 4 4 s 1 . the configuration is an exception to the

Type the letter that represents the correct location for each particle type below.

Why is permeable soil best for plants that need a lot of drainage?