Question

(a) State Law of constant composition
(b) Wrile electronic configuration of
Cr, Cu, Zn.​

Answer 1

a) According to law of constant composition , in a chemical substance , its constituent are always present in fix ratio by mass , whatever be the source and method of preparation . For example : In water , Hydrogen and oxygen are always present in ratio 1:8 by mass . It does not depend on the source of water taken or the method of its preparation .

This law is also called law of definite proportion and was given by Joseph L . Proust .

b) Electronic configuration of :

1) $\rm Cr_{24}$ = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

or

$\rm Cr_{24}$ = [Ar] 3d⁵ 4s¹

2) $\rm Cu_{29}$ = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s¹

or

$\rm Cu_{29}$ = [Ar] 3d¹⁰ 4s¹

3) $\rm Zn_{30}$ = 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s²

or

$\rm Zn_{30}$ = [Ar] 3d¹⁰ 4s²

The electronic configuration of Cr and Cu are exceptional case in which the electron half fills the outermost shell to gain stability as half filled and fully filled shells are more stable than partially filled .