Diagonal Relationship between Lithium (Li) and Magnesium (Mg)

In this article we will discuss about the diagonal relationship between Lithium (Li) and Magnesium (Mg) .

Before getting to the topic , you should know that what does this diagonal relationship is ? The answer is here : 

Diagonal Relationship:- In the periodic table the elements of same group exhibits similar properties but it was observed that some of the diagonally adjacent elements shows much similar properties which differs from the properties of elements of their group . Thus this property of diagonally adjacent elements of behaving similar to each other is called Diagonal Relationship .

In this article we will discuss about the diagonal relationship of Lithium (Li) and Magnesium (Mg) .

Diagonal Relationship between Li and Mg :-

In many respects , Lithium differs from the rest of the alkali metals and resembles Magnesium with which is diagonally related . It is because of similarity of ionic size of Li and Magnesium .

We can understand the abnormal behaviour of Lithium from alkali metals and similarity to Magnesium with the help of following points -

1. Lithium and Magnesium have high melting point than other elements in their respective group .

2. As similar to magnesium , Lithium is also a least reactive element among other alkali metals . The other alkali metals reacts vigorously with water while lithium is slowly attacked by water at 298 k similar to magnesium .

3. Showing similarity with magnesium , lithium is the only alkali metals which directly combines with nitrogen to give Li3N (Magnesium gives Mg3N2) which are further decomposed by water and gives ammonia (both lithium and magnesium gives ammonia on decomposition by water) .

4. On treating with oxygen , all the alkali metals except lithium first gives norm oxides which further combines with oxygen to form peroxide and superocides while Lithium gives the normal oxides only like magnesium .

5. Both lithium hydroxide and magnesium hydroxide are sparingly soluble in water while other alkali metal hydroxides are quite soluble in water .

6. The alkali metal hydroxides remains unaffected on heating , but in case of lithium hydroxide , it decomposes at red heat to form oxides .

7. The flourides , carbonates and phosphates of lithium and magnesium are sparingly soluble in water but the corresponding compounds of the other alkali metals are freely soluble .

8. The ions of Lithium and Magnesium have strong polarising power , therefore they have great tendency to form hydrates . Thus a number of lithium and magnesium salts are hydrated while the salts of other alkali metals are not hydrated .

The above were some points on the basis of which we can say that there is a diagonal relationship between Lithium (Li) and Magnesium (Mg)

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