Niyati

1. cation is written first in the formula. 2. oxidation number of a free element is always zero. 3. the oxidation number of a monoatomic ion eqauls the charge of the ion. na+ = +1, ca+2 = +2 4. usual oxidation number of  H= +1, O= -2,  group 1 = +1, group 2= +2, group 6= -2, group 7= -1. 5. the sum of all the oxidation numbers of all the atoms in a neutral compound is 0. 6. the sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion. for eg-  the sum of the oxidation numbers for SO4 2- is -2.

1. If the elctrostatic field created by the ligand point charges is isotropic(spherically symmterical), the enrgies of the d-orbitals will remain degenerate but will increase in energy uniformly. 2. IF, HOWEVER THE ELCTROSTATIC FIELD CREATED BY THE LIGAND IS OCTAHEDRAL, then the d-orbitals will split into two sets of degenerate energy, the t2g set and eg set. 3. t2g- stabilised(3-orbitals); eg- destabilised(2-orbbitals). 4. the energy separation between two split degenerate sets of orbitals is defined as crystal field splitting energy. 5. electrons occupy t2g set but the fourth electron has a choice to enter either t2g or eg set. although electron would enter a stabilised energy level, to do so would require additional energy to pair the electron with another electron in an already filled orbital. this additional energy is termed as the pairing energy, P.