Question

Write the complete electron configurations Cobal(Co) atom for its:

        1-its ground state
         2- an excited state       
2- Draw the orbital diagram for the complete electron configuration of Sulfur atom

3-Briefly explain how the following concepts are used in developing electron configuration of atoms: Hund’s rule and Pauli Exclusion principle.

      

Answer 1

1) Co - atomic no 27

ground state electron configuration:1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁷, 4s² or [Ar] 3d⁷ 4s².

an excited state electron configuration:1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁸, 4s¹ or [Ar] 3d⁸ 4s¹.

2) S - - atomic no 16

ground state  electron configuration:1s², 2s², 2p⁶, 3s², 3p⁴. (see image file)

3) Hund’s rule: When filling sublevels other than s, electrons are placed in individual orbitals before they are paired up. So when working with the p sublevel (px, py and pz), electrons first fill three degenorated orbitals first, then it will start pairing. In the case of d orbital (d_x,d_y,d_z,d_x2-y2 and d^_z2) first 5 electrons will occupy individual degenorated d subshel, then only incoming electron will pair up.

The Pauli Exclusion Principle states that, in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins. This means if one is assigned an up-spin ( +1/2), the other must be down-spin (-1/2).