Q9 of 56 Page 1

The elements 4Be, 12Mg and 20Ca, each having two valence electrons in their valence shells, are in periods 2, 3 and 4 respectively of the modern periodic table. Answer the following questions associated with these elements, giving reason in each case:

(a) In which group should they be?


(b) Which one of them is least reactive?


(c) Which one of them has take largest atomic size?

The electron configuration of elements are as follows:

Be – 2, 2


Ca – 2, 8, 8, 2


Mg – 2, 8, 2


4Be, 12Mg, 20Ca


(a) Since all the elements have same no. of valence electrons i.e. 2, so they all belongs to group 2.


(b) Since there are only 2 shells in Be due to which the forces of attraction between nucleus and its electrons is strong due to which it can’t lose electrons easily. Therefore, it is the least reactive.


(c) As Ca has maximum shells and therefore it will have largest atomic size.


More from this chapter

All 56 →
6

List any two advantages associated with water stored in the ground.

 7

What is meant by homologous series of carbon compounds? Classify the following carbon compounds into two homologous series and name them.

C3H4 C3H6 C4H6 C4H8 C5H8 C5H10

 11

List three distinguishing features between sexual and asexual types of reproduction, in tabular form.

 14

A pea plant with blue colour flower denoted by BB is cross-bred with a pea plant with white flower denoted by ww.

(a) What is the expected colour of the flowers in their F1progeny?


(b) What will be the percentage of plants bearing white flower in F2 generation, when the flowers of F1 plants were selfed?


(c) State the expected ratio of the genotype BB and Bw in the F2 progeny.