Question

What happens to the position of an element in the periodic table when it emits an alpha particle 

Answer 1

After emitting an alpha particle the daughter element occupies two places to the left of the parent element in the periodic table.

Reason: If a parent nucleus X becomes a new daughter nucleus Y as a result of -decay, then the -decay can be represented as:

\[\ce{\underset{\text{parent nucleus}}{^A_Z X} ->[Alpha decay] \underset{\text{Daughter nucleus}}{^{A-4}_{z-2}Y} + \underset{\text{α-particle}}{^4_2 He}}\]

Thus, the resulting nucleus has an atomic number equal to (Z-2). Hence, it shifts two places to the left of the parent element in the periodic table.

(b) After emitting a β

-particle, the daughter element occupies one place to the right of the parent element in the periodic table.

Reason: If a parent nucleus X becomes a new daughter nucleus Y as a result of -decay, then the -decay can be represented as:

\[\ce{\underset{\text{parent nucleus}}{^A_Z X} ->[β particle] \underset{\text{Daughter nucleus}}{^{A}_{z+1}Y} + \underset{\text{β-particle}}{^0_-1e}}\]

Thus, the resulting nucleus has an atomic number equal to (Z+1). Hence, it shifts one place to the right of the parent element in the periodic table.

(c) After emitting -radiation, the element occupies the same position in the periodic table.

Reason: If a parent nucleus X becomes a new daughter nucleus Y as a result of -decay, then the -decay can be represented as:

\[\ce{\underset{\text{parent nucleus}}{^A_Z X} ->[γ particle] \underset{\text{Daughter nucleus}}{^{A}_{z}Y} + \underset{\text{γ-particle}}{γ}}\]

Thus, the resulting nucleus has atomic number equal to Z. Hence, it occupies the same position as the parent element in the periodic table.