Group displacement law

$Group displacement law$

source : sciencehq.com

pharmalife.weebly.com

Soddy, Fajan & Russel gave a law, to know the position of new element formed after the emission of  alpha & beta particle. According to Group displacement law.

• If an α-particle is emitted by a radio active element from its nucleus, the atomic no. of new element or daughter element formed is decreased by 2 units & atomic weight is decreased by 4 units. Therefore  the position of new element formed is displaced by two groups towards the left in the periodic table

ZAM——>Z-2CM-4 +2He4 (α-particle)

• If a β–particle is emitted by a radioactive element, the atomic number of daughter element or new element is increased by one unit. Therefore the position of new element is displaced by one group towards the right in periodic table.

ZAM——> Z+1CM + -1β0 (β-particle)

• If an α-particle is emitted from the nucleus of radioactive element and then 2β-particles are emitted in next two transformations, the daughter element is an isotope of parent element. The daughter & parent element have the same atomic number. Hence according to Group displacement law position of daughter & parent element in the periodic table will remain same.

ZAM—–> ZAM-4 +2-1β0+2He4

• Group displacement law is not applicable to lanthanides & actinides. (f-block elements)

### Solution )

When α-particle is emitted, the atomic No. of new element is decreased by 2 units & atomic weight by 4 units. Its position is displaced by two group towards left in periodic table

84Po215 ——->    82Pb211+ 2He4(α-particle)

(VI Group)       (IV group)

New element 82Pb211 is present in IV group of periodic table.

1. 83x209—alpha—-> Y   – -beta–>   Z

(V group)                    (III group)    (IV group)

### Solution )

83x209 — alpha—–>81Y205  —beta——> 82Z205

(V group)         (III group)    (IV group)