. An element X belongs to 3rd period and group 13 of the Modern Periodic Table
(a) Determine the valence electrons and the valency of 'X'.
(b) Molecular formula of the compound formed when 'X' reacts with an element 'Y' (atomic number = 8).
(c) Write the name and formula of the compound formed when 'X' combines with chlorine.
Ans. X belongs to 3rd period and the 13th group.
(a) Since X belongs to 13th group, therefore its valence electrons = 3.
Valency of element X= 3
(b) When 'X' reacts with element 'Y':
:. Molecular formula of compound formed is X2Y3.
(c) Electronic configuration = 2, 8, 3
:. X is Aluminium (AI)
Atomic number of chlorine= 17
Electronic configuration = 2, 8, 7
No. of valence electrons = 7
Valency of chlorine= 8- 7 = 1