Co is the symbol for element cobalt. Atomic number of Co is 27. 1st shell has s orbital and can hold up to 2 electrons. 2nd shell has s and p orbital and can hold upto 8 electrons 3rd shell has s, p and d orbital and can hold upto 18 electrons In Co electronic configuration upto p orbital in 3rd energy shell is 1s² 2s² 2p⁶ 3s² 3p⁶ After 3p orbital, electrons start filling in the s orbital in 4th energy shell as 4s orbital has lower energy than 3d therefore it fills 4s before 3d, after it fills 2 electrons in 4s, remaining electrons fill 3d orbital
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁷ in the 3d subshell there are 7 electrons
The first 2 electrons are in the inner shell, and the other 6 are valence electrons. Oxygen needs 2 more electrons to fill its valence shell and satisfy the octet rule.
