Explanation
A Diagonal Relationship is said to exist between certain pairs of diagonally adjacent elements in the second and third periods of the periodic table. These pairs (Li & Mg, Be & Al, B & Si etc.) exhibit similar properties; for example, Boron and Silicon are both semiconductors, form halides that are hydrolyzed in water and have acidic oxides. Such a relationship occurs because crossing and descending the periodic table have opposing effects. On crossing a period of the periodic table, the size of the atoms decreases, and on descending a group the size of the atoms increases. Similarly, on moving along the period
the elements become progressively more covalent, less reducing and more electronegative, whereas on descending the group the elements become more ionic, more basic and less electronegative. Thus, on both descending a group and crossing by one element the changes cancel each other out, and elements with similar properties which have similar chemistry are often found - the atomic size, electronegativity, properties of compounds (and so forth) of the diagonal members are similar.
The chemistry of lithium is very similar to that of magnesium even though they are placed in different groups. Its reason is that the ratio of their charge to size is nearly the same
Hint: Half filled $$ \&$$ fully filled configurations are more stable due to exchange energy.
· The configuration of $$Li$$ is $$1s^{2}2s^{1}$$ . Adding one $$e^{-}$$ will fill its $$2s$$ subshell providing it extra stability.
· The configuration of $$Be$$ is $$1s^{2}2s^{2}$$ . Adding one $$e^{-}$$ will disturb its stable fully filled configuration. So, it is the least stable among all.
· The configuration of $$B$$ is $$ 1s^{2}2s^{2}2p^{1}$$. It does not have half-filled or fully filled configuration so adding one $$ e^{-}$$ will not disturb its stable configuration.
· The configuration of $$C$$ is $$ 1s^{2}2s^{2}2p^{2}$$. It does not have half-filled or fully filled configuration so adding one $$ e^{-}$$ its configuration becoes $$ 1s^2 2s^2 2p^3$$ that it is a half-filled configuration and becomes stable.
Correct Option : $$B$$.
Please disable the adBlock and continue. Thank you.