Explain the diagonal relation ship between Li and Mg - Chemistry - Classification of Elements and Periodicity in Properties

Question

Explain the diagonal relation ship between Li and Mg

Kirti Gogia · Accepted Answer

On moving diagonally in the modern periodic table the elements
show certain similarities This is due to the fact that on moving
across a period from left to right electropositivity of the atom
decreases On the other hand on moving down the group
electropositivity increases These two factors work in opposite
direction Hence the elements that are present diagonally to each
other have similar properties
Diagonal relationship is more noticeable in the second and third
period of the modern periodic table It is shown as under:-
<img alt="" src=
"https://s3mn%20mnimgs%20com/img/shared/discuss_editlive/2460467/2012_02_07_11_43_27/1739719%20png">
As a result of diagonal relationship the physical properties
such as the atomic size, electronegativity, density etc and
chemical properties of compounds such as reaction with water,
nitrogen, decomposition reactions etc are similar
For example: The similarities between Li and Mg as a result of
diagonal relationship are as follows:

Both are harder and lighter than the other elements in the
respective groups

Both react slowly with water; oxides of both are less soluble
in water; hydroxides of both decompose on heating

Both form nitrides (Li3N and
Mg3N2) by directly reacting with
nitrogen

Both do not form superoxide

On heating, carbonates of both give oxides and CO2;
hydrogen carbonates of both do not exist as solid

Chlorides of both (LiCl, MgCl2) are soluble in
ethanol, deliquescent, and crystallize as hydrates (LiCl
2H2O, MgCl2 8H2O)