Give reasons:
(i) Li & Mg show similar properties.
(ii) Alkali metals show +1 oxidation state.
(iii) Alkali metals have largest size in their period.
Answers
(i) There is a diagonal relationship existing between lithium and magnesium. That's why they both show similar properties. There are many reasons for this diagonal relationship
(a) In the periodic table, the elements from top to bottom in any particular group exhibit an ascending order of their electropositive nature. On the other hand, the elements from left to right, the same nature would be in decreasing order. This is one of the reason why diagonal elements like magnesium and lithium have similarities.
(b) Size of the atom in a group from top to bottom increases. This implies that the polarizing power of the elements in the group is in descending order. But, from left to right in a periodic table, the polarising power increases. This is another reason why lithium and magnesium are said to be strong elements and possess similarities
(ii) Alkali metals have only one electron in their outermost shell. When an alkali metal loses that single electron, it achieves stable configuration of a noble gas. Thus these alkali metals exhibit an oxidation state of +1.
(iii) Alkali metals are located at the extreme left side of the periodic table. The introduction of new valence shells begin from these alkali metals and then moves over to the remaining elements in the respective periods. Additionally, "alkali metals" have the lowest nuclear charge when compared to the other elements in the respective periods.
That is why the alkali metals are largest size when compared to the other elements in the respective periods.