Question

given below are some elements of the modern periodic table:-Be, F, Si ,K (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 your answer (iii)select two element that belong to the same period which of these two has bigger atomic size

Answer 1

(1).K has one electron in their outermost shell(1s2,2s2,2p6,3s2,3p6,4s1.
(2).none of them belongs to the same group.(k-1),(Be-2),(si-14),(F-17).(3).Be and F belongs to same period and Be is a bigger atomic size elements.because,from left to right in periods atomic radius decreases.

Answer 2

(i)K has one electron in its outermst shell.

E.C of K = 1s2 2s2 2p6 3s2 3p6 4s1

(ii) None of the are on the same group, as the no. of their valence electron are not same [no. of valence electron must be same to belong in the same group]

(iii) Be and F belong to the same period, as the no. of shell is same i.e 2.

Among them, Be is bigger in size as the nuclear attraction power is less compared to F. Because F has greater no. of protons than Be, resulting greater nuclear attraction, thus atomic radius of F is smaller than Be.