Question

Given below are some elements of modern parodic table. Atomic number
of the element is given below. 3
A (4), B (9), C (14), D (19), E (20)
(i) Which elements has one electron in outer most shell. Also write its
electronic configuration.
(ii) Which of two element belong to same group.
(iii) Which of two element belong to same period? Which one has higher
atomic radii?

Answer 1

Hope it helps........

Answer 2

Given elements are :
A  - 4 - Be-1s2 2s2
B-9 -F- 1s2  2s2 2p5
C-14-Si - 1s2 2s2 2p6 3s2 3p2
D-19-K - 1s2 2s2 2p6 3s2 3p6 4s1
E-20-Ca - 1s2 2s2 2p6 3s2 3p6 4s2


(i) Which elements has one electron in outer most shell.  -- element D

(ii) Which of two element belong to same group: B and E

iii) Which of two element belong to same period? Which one has higher
atomic radii? 
element D and E belong to same period . And Element D has more atomic radius .