Question

Given below are some elements of the modern periodic table:

            4Be, 9Fe,14Si, 19K, 20Ca

            (i)Select the element that has one electron in the outermost shell and write its electronic configuration.

            (ii)Select two elements that belong to the same group. Give reason for you answer.

            (iii)Select two elements that belong to the same period. Which one of the two has bigger atomic size

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Answer 1

Answer:

1. 19K potassium has 1 electron in the outermost shell. Its electronic configuration is 2,8,8,1.

2. Berylium ( 4 Be) and Calcium ( 20 Ca) belong to group 2. They both are alkaline earth metals and contain valency as 2 and hence, placed in group 2.

3. 26 Fe,19 K and 20Ca all belong to the 4th period. Moving left to right across a period, atomic radius usually decreases. Hence, K has the biggest atomic size as compared to 20Ca and 26 Fe.