Q10 of 40 Page 1

Na, Mg, and Al are the elements of the 3rd period of the Modern Periodic Table having group number 1, 2 and 13 respectively. Which one of these elements has the (a) highest valency, (b) largest atomic radius, and (c) maximum chemical reactivity? Justify your answer stating the reason for each.

Al has the highest valency as it has 3 valence electrons. Its atomic number is 13[2,8,3].

Na has a largest atomic radius as atomic radius decreases across a period from left to right.


Na as the tendency to lose electrons decreases across a period from left to right. So, Na is highly reactive as compared to Mg and Al.


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