(i) How many unpaired electrons are present in the ground state of Fe^(3+) (z=26), Mn^(2+) (z=25) and argon (z=18)? Explain about the significane of de Broglie equation.

(i) How many unpaired electrons are present in the ground state of Fe^

1.	(i) How many unpaired electrons are present in the ground state of Fe^(3+) (z=26), Mn^(2+) (z=25) and argon (z=18)? Explain about the significane of de Broglie equation.
Answer» Solution :(i) `Fe rarr Fe^(3+) + 3e^(-)` Fe(Z = 26)`Fe^(3+)` = number of electrons = 23 `2S^(2)2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(6) 4s^(2)` for Fe atom. `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(5)` for `Fe^(3+)` ion. So, it contain 5 UNPAIRED electrons. Mn (Z = 25). Electronic configuration is `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 4s^(2) 3d^(5)` `Mn rarr Mn^(2+) + 2e^(-)` Number of unpaired electrons in `Mn^(2+) = 5` Ar (Z = 18). Electronic configuration is `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6)` All orbitals are completely filled. So, no unpaired electrons in it. (ii) Significance of de Broglie equation: 1. `lamda = (h)/(mv)`This equation IMPLIES that a moving particle can be considered as a wave and a wave can exihibit the properties of a particle. 2. For a particle with high linear momentum (mv) the wavelength will be so small and cannot be observed. 3. For MICROSCOPIC particle such as an electron, the mass is the order of `10^(-31)` kg, hence the wavelength is much larger than the size of atom and it becomes significant. 4. For the electron, the de Broglie wavelength is significant and measurable while for the iron ball it is too small to MEASURE, hence it becomes insignificant.