Explain briefly how +2 states becomes more and more stable in the first half of the first row transition elements with increasing atomic number .

Explanation

(i) It can be easily observed that except Sc all other metals posses +2 oxidatin state.
(ii) Also , on moving from Sc to Mn, the atomic number increasing from 21 to 25
(iii) this means the number of electrons in the 3d- orbital also increases from 1 to 5 .
`Sc^(+2) = d^(1)`
`Ti^(+2) = d^(2)`
`V^(+2) = d^(3) `
`CrT^(+2) = d^(4)`
`Mn^(+2) = d^(s)`
(iv) + 2 Oxidation state is attained by the loss of the two 4 electrons by these metals
(v) Since the number of d electron in (+2) state also increases from `Ti^(+2) ` to `Mn^(+2)` the stability of +2 state increases
(vi) As a result d- orbital is becoming more and more half- filled .