Question

The element X in group 17 has 3 shells. If so, 

a. Write the sub shell electronic configuration of the element. 

b. Write the period number, 

c. What will be the chemical formula of the compound formed if the element X reacts with element Y of the third period which contains one electron in the p sub shell?

Answer 1

a. Three shells are K, L, M. The sub shells are 

1s, 2s, 2p, 3s, 3p, 3d 

Group number: 17 

Electrons in last shell: 7 

Shell electronic configuration: 2,8,7 

Sub-shell electronic configuration 1s² , 2s² , 2p⁶ , 3s² , 3p⁵ 

b. Period-3 

c. Y – Third period 

∴ shells – 3 

1 electron in p – sub shell 

Total electrons in valence shell 2+1=3 (2 electrons in s + 1 electron in p) 

Valency of x – 1(1 electron is recieved – electro negative atom) 

Valency of y – 3 (3 electrons are lost –electro positive atom) 

Therefore they combine to form compounds with chemical formula YX3

(Symbol of electropositive element first followed by electro negative element).