Question

What is a transition element with five d-block electrons in energy level 4?

Answer 1

Possible answers are Mn `25 Cr` 24 V # 23

Explanation:

Manganese 25 has a ground state electron configuration of `4s^2 3d^5`

This gives Manganese 5 electrons in the d block.

Chromium 24 has a ground state electron configuration of `4s^23d^4`

Chromium will hybridize one of the 4s electrons into the 3d block to achieve greater stability and ability to form bonds, giving it

`4s^1 3d^5`

This gives Chromium 5 electrons in the d block

Vandium 23 has a ground state of electron configuration of`4^2 3d^3`

Vandium can hybridize both of the 4s electrons ( not near as common as Chromium hybridizing. ) giving V `4s^0 3d^5`

This gives Vandium 5 electrons in the d block.

Mn is the most obvious answer to the element with 5 d block electrons but Cr and V are also possible answers.

Answer 2

Chromium and manganese.

Explanation:

Each period on the periodic table corresponds to the primary energy level, `"n"`, for the elements in the period. Chromium and manganese are in the fourth energy level, period 4, n=4. The ground state electron configuration of chromium is `["Ar"]"3d"^5"4s"^1`, and the ground state electron configuration of manganese is `["Ar"]"3d"^5"4s"^2`.

This is a website that gives the ground state electron configurations for all of the elements.
http://periodictable.com/Properties/A/ElectronConfigurationString.al.html

If you need a printable periodic table with the ground state electron configurations of the elements, check these sites.

https://www.nist.gov/pml/periodic-table-elements

https://www.vertex42.com/ExcelTemplates/periodic-table-of-elements.html