Am2+ ion has four electrons in the 3d subshell and is derived from a metal in the first transition metal series. what element might m be? elemental symbol:

Explanation:

Since it is given that the metal belongs to first transition metal series. Therefore, it is known that in first transition metal series the electrons are placed in 4s and 3d orbitals.

Also, oxidation number of this metal cation is +2 so, being the outermost shell electrons will be first removed from 4s shell. It is known that an s orbital can accommodate maximum of two electrons.

So, the configuration will be as [Ar] 3d^{4} 4s^{0}

Now, there are 4 electrons in 3d shell. Therefore, chromium has atomic number 24 and it contains 4 electrons in 3d shell after the formation of its cation.

Electronic configuration of chromium is as follows.

          Cr :  [Ar]

      : [Ar]

Thus, we can conclude that element "m" must be chromium.

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"